Five spring barley varieties resistant to race 24 of Puccinia striiformis were crossed with each other and with three susceptible varieties (Table 1) in almost all possible combinations. The F 2 generations and in two cases also the F 3, were inoculated in the greenhouse with race 24. F 2 generations of some of the crosses were, in addition, tested with race 24 in the field. Dependable classification of resistance and, consequently, unambiguous interpretation of results was possible only for the experiments carried out in the greenhouse. Although the field tests confirmed these results, they would not have been conclusive by themselves.The resistance of all of the five varieties studied is due to single recessive genes (Table 2). Three of the varieties have alleles at the same locus, the other two varieties have other resistance genes (Tables 3 and 4): 'Bigo' - yr, 'Ab. 14' - yr, 'BBA 2890' - yr; 'Abed Binder 12' - yr2; 'I 5' - yr3. The results suggest that the three genes are inherited independently, close linkage can be excluded.