Two groups of chlorophyll mutants of winter rye i.e. lethal and semilethal were compared in the present studies. Plants of the first group were characterized by pink orange or light violet colour of leaves at the seedlings stage. Plants with light green leaves, with yellow necrotic spots on leaves, or with white pattern and necrotic spots on leaves belonged to the second semilethal group. While plas-tids in pink and violet mutants were deprived of internal membrane organization in orange ones they had single thylakoids. In the second group of plants granal and intergranal thylakoids were present although the number of grana was reduced. The above changes in the plastid ultrastructure were accompanied by a lack of chlorophylls in pink, orange and light violet plants or strong reduction of both chlorophylls a and b in the remaining mutants. All the described features were inherited by single recessive genes.