The aims of the study were to investigate the prevalence of antibodies to Toxoplasma gondii in a group of patients bitten by cats, and also to determine if toxoplasmosis can be transferred by cat bite. Seventy-two patients who attended the emergency wards at 3 hospitals in Stockholm, Sweden, due to infection by cat bite, were investigated for specific IgM and IgG antibodies to T. gondii in the acute phase, as well as in the convalescent phase about 2 weeks later. Specific IgG antibodies to T. gondii (> or =8 IU/ml) were found in 17/72 patients (24%) in the acute phase. No case of seroconversion occurred. Patients who were bitten by their own cat had positive antibody titres to T. gondii significantly more often than those bitten by a foreign cat; 30% and 5%, respectively (p = 0.02). This suggests that regular contact with cats may contribute to the transmission of the parasite.