Toxoplasmosis in pregnant women can lead to congenital disease with severe neurological and ocular complications in the foetus. In 2006, we surveyed US obstetrician-gynaecologists to determine their knowledge and practices about toxoplasmosis prevention and testing. Questionnaires were mailed (four mailings) to a random sample of 1200 of the 33,354 members of the American College of Obstetricians and Gynecologists (ACOG). Of the 1200 surveyed, 502 (42%) responded. The respondents were similar to all ACOG members by gender, region of the country and practice type (P > 0.5), and age (respondents were slightly younger, mean 46 years versus 47 years). To prevent toxoplasmosis, most respondents indicated that they counsel pregnant women about cat litter (99.6%), but fewer counselled about eating undercooked meat (77.6%), handling raw meat (67.4%), gardening (65.4%) or washing fruits and vegetables (34.2%). Many (73.2%) respondents were not aware that some Toxoplasma IgM tests have had a high false positive rate, and most (91.2%) had not heard of the avidity test, which can help determine the timing of Toxoplasma gondii infection in relation to pregnancy. There is a need for more education about T. gondii serological testing, particularly the Toxoplasma avidity test. US obstetrician-gynaecologists are providing beneficial counselling to their patients, but could provide more information about undercooked meat and soil risks.