The authors studied offender, offense, and victim characteristics in a cohort of 111 adult female sex offenders comprising all female sex offenders known to the criminal justice authorities in the Netherlands between 1994 and 2005. In 77% of the cases, the female sex offenders had abused children; almost two thirds of the women had co-offended with a male co-offender. Their backgrounds are on average problematic with sexual abuse being prominent (31%); mental disorders were also prominent (59%). Using multiple correspondence analysis, the authors distinguished four prototypical offender types. They identified the young assaulter and the rapist who are relatively young solo offenders. Two prototypes, the psychologically disturbed co-offender and the passive mother, comprise older women. They mostly abused their own children together with their male/intimate partner. These prototypes partly overlap with previous typologies. The authors discuss implications for theory and treatment. © The Author(s) 2010.