Several different expressions of male sterility were observed in the plants sampled for the study of pollen and anther development in the third substitution backcross generation to intermediate wheatgrass. These included (1) pollen abortion following engorgement with starch, (2) abortion of microspores with exine abnormalities (found most often in plants with a high degree of meiotic irregularities), (3) abortion of microspores with normal exines, (4) release at anther dehiscence of normal-appearing late vacuolate microspores, (5) enlargement of one of the parietal layers of the anther, and (6) tapetal abnormalities, including orbicular wall malformations. Anthers from plants which were male sterile or partially male sterile and meiotically irregular were shorter than anthers from fertile or partially male-sterile, meiotically regular plants.Definite statements about specific causes of the male sterility could not be made. Meiotic irregularities may be involved in some of the male sterility, and exine malformations appeared to be directly related to sterile microspores. Tapetal disturbances were observed infrequently. Probably the consequences of several factors were observed in the backcross material.