Helisoma trivolvis (Gastropoda) from 10 lentic ecosystems in New Jersey, U.S.A., was investigated on a seasonal basis from Fall 2003 to Fall 2004. A total of 6,766 H. trivolvis (5.7-22.9 mm shell diameter) was examined by isolation, and 8 different types of cercariae were recovered. Prevalence data from the 10 study sites showed cercariae of Echinostoma trivolvis from 9 sites (0.9–27.8%), cercariae of Zygocotyle lunata from 6 sites (0.1–7.7%), armatae cercariae from 4 sites (0.4–6.8%), brevifurcate apharyngeate cercariae from 4 sites (0.4–3.3%), longifurcate pharyngeate cercariae from 4 sites (0.002–3.6%), vivax cercariae from 2 sites (0.9–1.0%), brevifurcate pharyngeate cercariae from 1 site (0.6–1.1%), and gymnocephalous cercariae from 1 site (0.001%). The study showed that H. trivolvis is host to various different larval trematodes in New Jersey, and prevalence of digenean infections is affected by seasonality.