During 1954-1960, 2005 mammals of 18 species collected at the Patuxent Wildlife Research Center, Maryland, were examined for trypanosomes. T. cruzi was found in 10 raccoons between October 31 and November 30. Infection occurred in 2 percent of all raccoons sampled, and in 11.3 percent of the 80 raccoons sampled in November. Examination was by direct smears, stained smears and cultures of heart blood. Although, in previous studies, at least two experimentally infected raccoons exhibited extended parasitemia (14 and 8 weeks), no such continuing parasitemia was observed in the natural infections. No trypanosomes were found in any of the other mammals examined.