This paper presents the first detailed study on pathogenic variability in Rhynchosporium secalis in Ethiopia. Twenty four isolates of R. secalis, collected from Arsi, Bale and Shoa, major barley growing locations in Ethiopia, were tested on ten differential host cultivars, with known genes for resistance to the disease. The most frequent pathotypes were those inducing susceptible reactions on cvs Steudelli and Kitchen and the least complex pathotype identified was able to induce a susceptible reaction on these two cultivars only. Pathotypes 16 and 7 were the most complex and were able to induce susceptible reactions on 10 and 9 of the differential host cultivars respectively. These pathotypes were collected from research stations and were isolated from improved barley cultivars belonging to the malting barley type. The most frequet pathotype was pathotype 6 which was represented by four isolates from different locations in Arsi, Bale and Shoa. Pathogenic variation was detected amongst spores collected from the same field and from the same geographical location. The most effective resistance genes were those possessed by Turk, La-Mesita, Bey, Nigrinudum, Jet and Forrajera.