BACKGROUND Although cocaine use in women has increased substantially over the past half-century, we understand little about the aetiology in women of cocaine use and abuse, and know almost nothing about the role of genetic factors. METHODS We obtained by telephone interview a history of lifetime cocaine use, abuse and dependence from 1934 individual twins from female-female pairs ascertained through a population-based registry, including both members of 485 monozygotic (MZ) and 335 dizygotic (DZ) pairs. RESULTS The prevalence of lifetime cocaine use, abuse and dependence were 14.0%, 3.3% and 2.3%. Probandwise concordance rates, in MZ and DZ twins, respectively, were: cocaine use 54% and 42%; cocaine abuse 47% and 8% and cocaine dependence 35% and 0%. In MZ and DZ twins, odds ratios were: cocaine use 14.2 and 6.7 and cocaine abuse 40.8 and 2.7. Biometrical model-fitting suggested that twin resemblance for liability to cocaine use was due to both genetic and familial-environmental factors while twin resemblance for cocaine abuse and symptoms of dependence was due solely to genetic factors. Estimated heritabilities were: cocaine use 0.39, cocaine abuse 0.79 and symptoms of dependence 0.65. CONCLUSIONS The vulnerability to cocaine use and particularly cocaine abuse and dependence in women is substantially influenced by genetic factors.