The host specificity of R. sanguineus (Latr.), 1806, sens, sir., and R. secundus Feldman-Muhsam, 1952, in Israel was studied.It was found that 81 per cent, of R. sanguineus, sens, lat., found on the dog was R. sanguineus, sens, str., and 19 per cent. R. secundus, whereas on cattle, sheep and goats, 97, 94 and 91 per cent., respectively, were R. secundus and the remainder R. sanguineus, sens. str.It is suggested that this situation exists also in other countries in the Near East, since R. secundus was very common in material from Algeria, Turkey, Yugoslavia and Iraq.The problem of transmission of disease by R. sanguineus, sens, lat., should be re-investigated in the light of recent taxonomic data.