Five hundred and sixty seven sera of healthy house cats aged 3 months to 7 years, were examined for the presence of anti-toxoplasma antibodies by indirect immunofluorescence assay and compared to SAG1 and TLA enzyme linked immunosorbent assays as alternative test. Twenty-five percent of cats tested positive for IgG and/or IgM. Seroprevalence increased with age from 2% below 12 months of age up to 44% at age 7. Sensitivities of SAG1 and TLA ELISA were 84.1% and 88.6%, respectively. Peak levels in seroprevalence were correlated to increased IgG titers in TLA ELISA. Our results suggest that T. gondii infections are common in house cats and that there is a high chance for a negative cat to seroconvert in its second life-year.