An unprecedented pocket of intestinal schistosomiasis was discovered in the Republic of Djibouti in 1997. The first cases were diagnosed in French and Djiboutian tourists who presented initial symptoms of bilharzian infection after bathing in the fresh-water basin under Hassan Gari Bira Falls, near Randa. Seventeen cases were subsequently confirmed by detection of anti-schistosome antibodies using indirect hemagglutination (IH) and indirect immunofluorescence (IIF) and/or detection of Schistosoma mansoni eggs in the stool. Further testing was performed in 35 village inhabitants, mostly children, who had been exposed by bathing in the basin. The IH reaction was positive in 28 patients (80 p. 100) including 17 (49 p. 100) with levels greater than 1/64. In 92 p. 100 of cases, IH findings were confirmed by IIF which indicated that association with hypereosinophilia was common. Schistosoma mansoni eggs were found in stools from 7 patients (19 p. 100) who generally displayed mild hypereosinophilia. Information concerning the zone of risk was distributed and control measures were undertaken as widely as possible in Djibouti and abroad.