White mice infected with Toxoplasma gondii (RH strain) and treated for 21 days with various peroral doses of spiramycin (R) and sulfametoxydiazine (S) were observed for 14 days after the administration of the drugs with the diet. The surviving animals treated with peroral doses of 300 mg/kg were found to be Toxoplasma carriers. The remaining mice treated with S (100 mg/kg), S (100 mg/kg) combined with R (100 mg/kg), or S (75 mg/kg) combined with R (300 mg/kg) survived the period of treatment, but succumbed after the discontinuation of the drugs; only few animals survived the 10-day follow-up period and they were not Toxoplasma carriers.