Cats excreted the protozoan Toxoplasma gondii in feces, generally between 5 to 12 days after ingesting mice with chronic toxoplasmosis. Toxoplasma gondii and eggs of the nematode Toxocara cati occurring together could be separated by washing them through sieves that retained the eggs. This finding negates the postulated role of Toxocara cati in the transmission of toxoplasmosis.