Abstract: Effect of different seed frequencies on infection severity of Rhynchosporium secalis and some yield components was investigated on Blenhaim barley cv. sown with six different densities. The firs sowing density was 300 seeds m-2 and 100 plus seeds m-2 was added for each later sowing. The last sowing frequency was 800 seeds m-2. Severe leaf scald was displayed in all infected plots. The average severity of disease in infected plots was about 71%. Exception of some sowing frequencies, grain yield generally increased in both control and infected plots dependent upon sowing frequencies increased. Thousand grain weight, however, generally decreased in both plots depending on seed densities increased. Compared to the control, important yield looses were observed in each sowing frequency of infected plots. The highest yield of the infected plots was lesser than the lowest yields of the control plots.