Oral Sex or oral-genital sex means both mouth contact with vagina, which is called cunnilingus, and mouth contact with penis, which is called fellatio. Cunnilingus comes from a Latin word for vulva (a woman's exterior sex organs), cunnus, and from Latin word for licking, lingere. Fellatio comes from Latin word fellare, meaning to suck. Either form of oral sex can be done with one partner stimulating other individually, or both partners can stimulate each other's genitals simultaneously. Oral sex given simultaneously is commonly called 69, or, French translation, soixante-neuf. This is because body position of a couple having mutual oral sex resembles numeral 69. Cunnilingus and fellatio are common sexual behaviors for both same sex couples and couples of different sexes. There are various combinations of positions and techniques used in oral sex, but it is mouth and tongue that provide pleasure in all cases. Kissing, licking, sucking and nibbling can feel good anywhere on genitals of both men and women. The pressure (light, firm, and in between), speed (fast, slow, or changing), and type of motion used can be varied endlessly to produce different sensations. In both practices, warm, moist feeling of mouth and tongue on genitals can be very erotic. Some enjoy a teasing, stop-start approach, while others prefer a more steady type of stimulation. In one fellatio technique, known as Snaky-Lick Trick, "trick" is to tease underside of penis head almost imperceptibly with very tip of tongue, just making ever so slight tongue contact with this sensitive area in one light upward lick, and then backing off for about fifteen seconds between each lick. This trick has been said to result in a powerful ejaculation in a very short time. Other methods of fellatio include sucking glans or shaft of penis by engulfing it in mouth, licking at various parts of penis and scrotum, or nibbling anywhere along genitals. Many men enjoy having scrotum lightly stroked during fellatio and area just beneath scrotum is often quite sensitive to touch or oral massage.

Some people are uncomfortable performing fellatio because they have a sensation of gagging when they take erect penis into their mouth. This real physiological event, known as gag reflex, is triggered by pressure at back of tongue or in throat. If a man, in his excited state, pushes his penis too far into his partner's mouth, gag reflex may take over. One way to avoid this problem is for person giving oral sex to grasp penis along shaft to control how much of it enters mouth. Another common objection to fellatio is having man ejaculate in his partner's mouth. A couple can agree in advance to have man remove his penis from his partner's mouth before ejaculation. Others don't mind. They either rinse ejaculate from their mouth right away or they swallow it. The ejaculate, on average about 4 cc, consists of proteins and sugars and reportedly contains less than 36 calories.

Cunnilingus, like fellatio, can be performed in many ways. Women's preferences vary, but commonly enjoyed techniques include gentle tongue movements over clitoris, more rapid, focused licking, or sucking clitoris either gently or in a rougher fashion. Other forms that women enjoy are oral stimulation of clitoris combined with fingering of vagina; licking and kissing of lips just outside vagina; having tongue thrust in and out of vaginal opening; and having the clitoris stimulated by hand (her own or her partner's) while oral stimulation is directed at other parts of genitals.

Not everyone has or enjoys oral sex. Many people who try it enjoy oral sex, but others have reservations about it. These reservations tend to fall into three arenas: first, that oral sex is unhygienic; second, that there is a taboo against it; third, that it is not a true expression of femininity or masculinity.

With regard to matter of hygiene and oral sex, neither vaginal fluid nor semen is harmful in any way. This of course is true only in persons who are not infected with a sexually transmitted disease (STD). Everyone should be sure that they themselves and their partners are free from STDs before engaging in any sexual activity. No disease can be passed by oral sex that wouldn't be transmitted by any other kind of sex. If one partner has a STD other is likely to catch it whatever they do together sexually. In short, oral sex between healthy people is safe and clean. Another hygiene aspect that concerns some people is genital odor. Simply washing genitals is sufficient to prepare you for any sex, including oral sex. It is not necessary for women to douche before having oral sex, but some women choose to do so. However, douching can wash away helpful bacteria that naturally protect vagina. In addition to a man's natural genital odors, genitals often take on smells of recently eaten foods. As with women, thorough washing can reduce this odor, and besides, many people find some degree of genital odor in their partner stimulating.

The notion that oral sex is taboo discourages some people from ever trying it. Oral sex has long been frowned upon and often deemed illegal. The basis for social disapproval and legal restrictions lies in age-old religious prohibitions, which to some are still very powerful. People who accept and practice almost any of major Western religions can refore feel confused and guilty about engaging in oral sex, despite their knowledge that it is a safe and appropriate form of sexual expression. In end, each individual must decide for him or her self whether to stick to teachings of his or her religion or to act in favor of what seems personally right for them.

For some people, the issue is not conflict with their religious beliefs as much as it is a belief that it somehow compromises their masculinity or femininity. Some people incorrectly think that cunnilingus and fellatio are homosexual acts, even if experienced by heterosexual couples. While homosexual couples do engage in oral sex, so do a majority of heterosexual couples. The activity itself is neither homosexual nor heterosexual. Apart form misconception about oral sex and homosexuality, women sometimes feel that performing oral sex can make them feel submissive, as if they are giving a service and are thereby inferior. Men sometimes feel that performing oral sex on their partner reduces their masculinity because their penis is not involved. Couples should openly discuss these issues, and if necessary seek help of a qualified therapist.

Fortunately, many people are free of negative feelings about oral sex and have chosen to include it in their sexual repertoire. However, it is just as okay to choose not to participate in oral sex as it is to do so. Oral sex, just like any other sexual behavior, is a matter of personal preference.