Objective. The aims of this study were to examine the associations between alcohol misuse and measures of early onset sexual activity and sexual risk-taking behaviors during adolescence and the extent to which any association between these two sets of behaviors could be explained by common risk factors that predisposed individuals to both outcomes. Method. Data were gathered during the course of a 16-year longitudinal study of a birth cohort of 953 New Zealand children and included: (1) self-report measures of early onset sexual activity (before the age of 16 years), multiple partners (three or more), and unprotected intercourse during the interval from 15 to 16 years; and (2) prospectively measured risk factors, including social background, childhood adversity, novelty seeking, and affiliations with delinquent peers. Results. Adolescents who reported misusing alcohol had odds of early onset sexual activity, multiple partners, and unprotected intercourse that were 6.1 to 23.0 times those of young people who did not misuse alcohol. After adjustment for common or correlated risk factors, the adjusted odds ratios between alcohol misuse and early onset sexual activity and unprotected intercourse were reduced but remained statistically significant. However, no significant association between alcohol misuse and multiple partners was found after adjustment for common or correlated risk factors. Conclusions. Much of the apparent association between alcohol misuse and teenage sexual activity and risk taking seems to arise through the influence of common family, individual, and peer factors. However, alcohol misuse may also place teenagers at greater risk of initiating early onset sexual intercourse and engaging in unprotected intercourse.