Résumé : The classical hematological test (lymphocytes counts) was applied to 5 herds of cattle where the enzootic form of bovine leukemia was diagnosed. In the same five herds, a search for antibodies directed against bovine leukemia virus (BLV) p 24 was carried out using an agar gel immunodiffusion (AGID) technique. Among the 245 animals screened, 30 reacted positively to both tests, 11 were positive by hematological test only and 15 were positive by serological test only. From these results we would advise to eliminate from so heavily infected herds, all the animals showing abnormal blood pictures and all these reacting positively to the immunological test. © 1976.