The abuse of alcohol and illicit drugs during pregnancy is associated with poor birth outcomes, child abuse, and increased infant mortality. This report describes women who gave birth in the state of Washington in the year July 1, 1991 through June 30, 1992 and identifies a group of women who abused substances while they were pregnant or in the year postpartum. The demographic characteristics and birth outcomes of substance abusers are examined, and substance abusers who received prenatal substance abuse treatment are compared to those who did not receive treatment. This study also explores the relationships between the amount and type of treatment received and maternal characteristics and birth outcomes.