This cross-sectional study of 420 women in two public maternity hospitals from August 2004 to May 2005 evaluated the application of a prenatal toxoplasmosis serological screening protocol in Belo Horizonte, Minas Gerais State, Brazil, and the information provided to susceptible pregnant women. Ninety-eight percent of women received prenatal care and 97% underwent the initial serological screening test, at an average of 16 weeks gestational age. The initial testing identified 163 women as susceptible to toxoplasmosis: 44% of these did not undergo repeat serological testing, and 42% of them did not remember having received information on the prevention of toxoplasmosis infection. Early prenatal care and a high number of prenatal visits were associated with repeat serological testing and orientation regarding its implications. Orientation on risk factors included: avoiding contact with cats (95%), not handling or eating raw meat (70%), and washing vegetables carefully before consumption (53%). Inadequate adherence to the prenatal screening protocol for toxoplasmosis, as detected in this study, may be generating health system costs without a corresponding improvement in the quality of perinatal care.