Exposure to one or more serovars of Leptospira interrogans was observed in five of six sampled elk (Cervus elaphus roosevelti) killed in November 1993, from an isolated herd in southwest Washington, USA (46 degrees 45'N, 123 degrees 6'W). In April 1994, exposure to L. interrogans serovars was documented in nine of 11 captured cow elk from the same herd. Leptospires were not isolated from any of the exposed elk, and 10 of the 11 cows were pregnant. The high seroprevalence is evidence that exposure is widespread in the herd. Local productivity of elk was high, however, and the surrounding topography was not conducive for transmission to other elk populations.