Between 1974 and 1985, 10 patients were studied who presented with either gastrointestinal complaints or unexplained peripheral blood eosinophilia, and had eggs typical for N. salmincola recovered from their stools. Clinical findings in 8 of the 10 included increased frequency of bowel movements or diarrhea (6), peripheral blood eosinophilia (6), abdominal discomfort (5), nausea and vomiting (3), weight loss (2), and fatigue (2). Two were asymptomatic. Eight recalled eating fish prior to the onset of symptoms. Anthelminthic treatment consisting of three 2-g doses of niclosamide (2 patients) or two 50 mg/kg doses of bithionol (1 patient) proved effective. In the remaining individuals symptoms resolved slowly over several months.