Trends in sexual risk behavior among high school students--United States, 1990, 1991, and 1993.
D000293:Adolescent; D017280:Condoms; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D011247:Pregnancy; D011253:Pregnancy in Adolescence; D012309:Risk-Taking; D012725:Sexual Behavior / Q000706:statistics & numerical data*; D012749:Sexually Transmitted Diseases; D013334:Students; D014481:United States