116 Catholic (50 9th graders and 66 12th graders) and 92 public high school students (52 9th graders and 40 12th graders) completed questionnaires concerning sexual knowledge and information about sexual activity. Analysis indicates that 33% of the Catholic and 73% of the public 12th graders had previous sexual experience. The Catholic school 12th graders had significantly higher scores on a sex knowledge test than the public school students, however, there were no significant correlations between these scores and sexual activity for either school. The factors that students said encouraged sexual experimentation included curiosity, need for love, and peer pressure, while the factors that discouraged these behaviors were fear of pregnancy and sexually transmissible diseases. Fear of contracting AIDS and religious beliefs did not strongly influence sexual behavior.