The prevalence of Toxoplasma gondii was determined in wild mammals in the Czech Republic from 1981 to 1990. The biological prevalence of T. gondii was <1% in insectivores (n = 578), 12% in carnivores (n = 112), 1% in rodents except muskrats (Ondatra zibethicus) (n = 5,163), 24% in muskrats (n = 437), 5% in lagomorphs (n = 293), 0% in ruminants (n = 456), and 2% in wild boars (Sus scrofa) (n = 136). The seroprevalence (Sabin-Feldman dye test, titre ≥ 1:4) of T. gondii was 15% in ruminants (n = 421), and 15% in wild boars (n = 124). Antibodies to T. gondii also were found in four of 10 carnivores. Toxoplasmosis is a common infection in wild mammals from the Czech Republic, but its prevalence varies considerable according to taxonomic groups and different localities where wild mammals live.