This study presents a cross-sectional examination of the independent contribution of pubertal maturation timing to heterosexual activity among Chinese adolescents. A standardized self-administered questionnaire was designed to obtain information on a spectrum of physical heterosexual behaviors from dating to sexual intercourse, age at first nocturnal ejaculation in boys, age at menarche in girls, and several psychosocial variables that might be associated with sexual behavior in adolescents. A total of 4,116 students aged from 14 to 18 years (2,175 boys and 1,941 girls) were recruited in the Youth Sexuality Survey of the Hong Kong Family Planning Association in 1996-97. When groups were defined as "early," "average," and "late maturers," among boys, early maturers were youngest to report dating and to have sexual intercourse, followed by average and late maturers. Among girls, late maturers were slower to date and have sexual intercourse, but early maturers showed no difference from average maturers. Age of maturation was significantly lower for those reporting all heterosexual behaviors for both sexes. Our findings illustrate culture's moderation of the expression of biological differences.