The actual sexual activity that takes place in a sex offense which involves a second person may range from no physical contact of any kind to vaginal coitus. Between these two extremes lies a wide area of possible behavior. This includes touching, casual or more extensive petting (genital or nongenital), mouth-genital contacts (mouth-penis or mouth-vulva), and attempted coitus. Supplementary sexual techniques may extend to anal coitus, either heterosexual or homosexual, or there may have been a general physical attack with underlying sexual content, even though no specific sexual behavior occurred. When one classifies the exact sexual activity in each of the over 2,000 offenses on which such data are available in the present study, instances of all these types of behavior are found. The incidence with which they were reported varies widely among the general types of offenses and more particularly among the age-of-object subclasses. Before classifying these data the heterosexual techniques were arranged in the following order of priority: (1) coitus, (2) attempted coitus, (3) mouth-genital contacts, (4) genital petting, and (5) simple or nongenital petting. Each offense was assigned to a single sexual technique classification, except in the case of mouth-genital and anal contacts occurring together in homosexual offenses, which are discussed later. Thus, if coitus occurred, the offense is classed as basically coital, even though various types of petting, genital or nongenital, may have accompanied the intercourse. For the noncoital offenses, the behavior that was specified as constituting the offense was used for tabulation purposes, even though other sexual activity may have also occurred. Omitted at this point in the analysis are, of course, the sex offenses which did not have a specific person, male or female, as an object of the offense. These comprise somewhat over 1 per cent of the total sample and include cases such as masquerading, fetish theft, and zoophilia.