Because many teenagers and young adults fail to use condoms correctly and consistently, the number of sexual partners they have is an important risk factor for sexually transmitted diseases, including HIV. Identifying factors that are associated with having multiple partners can help in the design of disease interventions. Data on 8,450 males and females aged 14-22 who participated in the 1992 Youth Risk Behavior Survey were used to examine the prevalence of and factors associated with young people's having multiple partners. In all, 63% of female respondents and 64% of males were sexually experienced. Among those who had had sex during the three months before the survey, 15% and 35%, respectively, had had two or more partners during that period. At each age, the majority of sexually experienced respondents had had more than one lifetime partner; between ages 14 and 21, the proportion who had had six or more rose from 8% to 31% among females and from 14% to 45% among males. In logistic regression analyses, alcohol use, illicit drug use and young age at first coitus were associated with increased odds that females had had two or more partners in the previous three months, and being married lowered the odds; black or Hispanic race or ethnicity, alcohol use and young age at first coitus increased the odds for males, and being married reduced the odds. As the number of reported alcohol-related behaviors increased, the adjusted proportion of respondents who had recently had multiple partners rose from 8% to 48% among females and from 23% to 61% among men. The strong association between alcohol use and having multiple sexual partners underscores the need to educate young people about the effects of alcohol on partner choice and the risk of infection with sexually transmitted diseases.