Objectives: To estimate the prevalence of illicit drug use in young Australian women, determine their patterns of drug use and identify associated risk factors. Methods: Data were collected in 2000 as part of the second survey of the youngest cohort in the Australian Longitudinal Study on Women's Health (n = 9512). Results: Among women aged 22-27 years, 58% reported having used an illicit drug at some time with most (57%) having used cannabis. Amphetamines (16%), ecstasy/designer drugs (15%) and LSD (14%) were the next three most commonly used drugs. Four different patterns of drug use were identified: past users of cannabis only (39%); current users of cannabis only (17%); past multiple drug users (13%) and current multiple drug users (31%). Living in a defacto relationship or never being married, living with non-family members, a history of physical abuse, sexual intercourse, smoking and binge drinking were associated significantly with exclusive use of cannabis and with use of multiple drugs compared to never using illicit drugs. Living with a partner, experience of sexual or emotional abuse, pregnancy, diagnosis of depression and taking sleeping medication were associated significantly with being a multiple drug user, but not for exclusive cannabis use. Multiple drug users had, on average, used cannabis 2-3 years before using any other drug. Conclusions: Given the strong association found between smoking, heavy drinking and drug use of varied patterns, public health initiatives targeted at preventing young women from smoking and drinking should additionally target illicit drug use.