Of the 55 lemmings captured in northern Finland in 1998, five had disseminated Hepatozoon sp. infection. Besides lungs, meronts were seen in the heart, kidney, liver and/or spleen. In the lungs, also visible were dizoic cysts, and merozoites engulfed by macrophages in a microgranuloma. The trypomastigotes detected in the plasma of eight of the lemmings differed in size, and in other morphological characteristics from those seen in this host species elsewhere. The mean hematocrit of the lemmings with disseminated hepatozoonosis was lower (39.6) than that reported from wild lemmings with no noticeable parasites (45), but the hematocrit values of the Trypanosoma sp. infected lemmings were within the normal range.