PIP: This study examined the role of family environment in determining early or later adolescent sexual behavior. Data were obtained from a 2-wave panel survey during 1989-1990, in the Brighton and Hove areas of Sussex, England. Interviews were conducted among 302 mother-adolescent pairs in the first wave and 255 pairs in the second follow-up wave. The study explored the links between intrafamily conflict (IC) and parent characteristics and adolescent sexual behavior to determine how effective selected factors are in preventing early sex. The theoretical model relates variables to sex at 2 time periods with IC as an intervening variable. The model accounted for 44% of the variance in the amount of IC. Key factors were a mother's suspicion that her child has had sex, the effort put into maintaining good relationships, and the importance attached to child discipline. 23% of the variance in permissiveness was related to adolescent age and religiosity and maternal religiosity. 37% of sexual experience at Time 1 was explained by the duration of the sexual experience, adolescent's age, and adolescent's permissiveness. The likelihood of Time 2 sexual experience was explained by older mothers, more permissive mothers, steady relationships at Time 1, and mother-child intrafamily conflict. Findings suggest that a good argument over matters one cares about is effective in bringing about desired results. An increase in better intrafamily relations did not lead to later sexual experience. Parents may sacrifice clarity as to what they expect from their children as a trade-off for good parent-child relationships.