In October 1978, a large family cluster of acute toxoplasmosis was identified in northern California. Indirect fluorescent IgM antibody tests showed that ten of 24 members of an extended family had serological evidence of acute Toxoplasma infection. The index case had retinochoroiditis; the other nine persons had asymptomatic infections. All ten seropositive persons had recently consumed raw goat's milk from the family herd as compared with no consumption of raw milk by the 14 persons with negative results. No dietary item or other risk factors were as strongly associated with positive serological test results as raw milk consumption. Although ingestion of soil-transmitted oocysts could not be ruled out unequivocally as the source of infection, the data suggest that drinking raw milk from infected goats might be another possible vehicle for the transmission of toxoplasmosis.