Serovars of Lisreria l1Iollocyrogelles were determined. Sera of aborted samples (200) were collected from different hospitals in Tehran and were tested serologically by immunofluorescent antibody methods (IF tests). 137 positive sera were identified. Positive sera were tested against 12 serovars of Listeria l1Iollocytogelles separately. Titers of antibody in patients' sera for all serovars were determined. The results showed that the dominant serovars of L.l1Iollocyrogelles which caused listeriosis in the samples were 4b, la, 2 and 3. None of the sera had antibodies against serovars 4a, oa or (ib. Some of the sera which had high titers of antibody against dominant serovars (4b, I a, 2 and 3), showed a faint result with serovars 4d, 4e,5 and 7.