The eytological basis of pollen abortion was investigated in rice genetic male sterile(GMS) lines controlled by single recessive genes. Four types, namely stainable pollen abor-tion (SPA), partial pollen abortion (PPA), complete pollen abortion (CPA), and no pollen(NP), were compared with the original cultivar M-101. Observations on chromosome beha-vior and tetrad analysis at meiosis showed that apparent chromosome aberrationswere closely related to the sterility in these GMS lines. The cytological abnor-malities occurring during the pollen development in these rice GMS lines were more pro-found and extensive than those reported in cytoplasmic male sterile (CMS) rice. At leastthirteen kinds of abnormalities were seen from the pre-meiotic stages to post-meiotic stagesin this study. The existence of microsporocytic pseudoplasmodium, sticking pollen, andpollen dissolution implied that abnormalities were occurring simultaneously in the anther walllayers, particularly in the tapetum. The eytological basis of pollen abortion was investigated in rice genetic male sterile (GMS) lines controlled by single recessive genes. Four types, stainable pollen abortion (SPA), partial pollen abortion (PPA), complete pollen abortion (CPA) and no pollen (NP), were compared with the original cultivar M-101. Observations on chromosome beha-vior and tetrad analysis at meiosis showed that apparent chromosome aberrationswere closely related to the sterility in these GMS lines. The cytological abnor-malities occurring during the pollen development in these rice GMS lines were more pro-found and extensive than those reported in cytoplasmic male sterile (CMS) rice. At leastthirteen kinds of abnormalities were seen from the pre-meiotic stages to post-meiotic stagesin this study. The existence of microsporocytic pseudoplasmodium, sticking pollen, and pollen dissolution implied that abnormalities were occurring simultaneously in the anther walllayers, particularly in the tapetum.