Abstract: Young panicles from ten rice materials, Zhenshan 97A (WA type cytoplasmic male_sterile (CMS) line, indica), Zhenshan 97B (WA type maintainer line, indica), IR24, IR26, Taiyin 1, Minghui 63 (WA type restorer line, indica), Hongyuan A (HL type CMS line,indica), Baoyuan A (BT type CMS line, indica), Nongken 58s (photoperiod_sensitive genic male_sterile rice (PGMR), japonica) and W6154s (thermosensitive genic male_sterile rice (TGMR), indica), were cultured on different media. Regenerated plants were obtained. Pollen fertility was examined. Male sterile variation frequency and factors influencing the in vitro screening of male-sterile variants are discussed. The main results are as follows: 29 cases of male_sterile variants in five rice materials, Zhenshan 97B, Hongyuan A, Baoyuan A, W6154s and IR26, were found, in which 24 cases belonged to R1 generation (regenerated plants from rice somaclones), and five to R2 generation (plants from first self_pollination, viz. progeny obtained by self_fertilizing the regenerated plants). 2*!368 regenerated plants were obtained in R1 generation, the male_sterile variation frequency was 1.02%(0.96～1.08%). Male-sterile variants were found in Zhenshan 97B and Taiyin 1 in R2 generation,and the average male_sterile variation frequency in Zhenshan 97B and Taiyin 1 was 2.22% and 1.89% respectively. Abortive pollen of rice could be classified into four types: pollenfree type (PFT), typicalabortion type (TAT), sphericalabortion type (SpAT) and stainedabortion type (StAT). The phenomenon that the type of pollen abortion could change from one to another through tissue culture was found in rice somaclones in R1 generation. One chimera was obtained from R1 regenerated plants of IR26 and Minghui 63 respectively. Fertility segregation was found in R 2 generation of Taiyin 1 and Zhenshan 97B. Genotype was the main factor in the course of inducing male_sterile variants. Male-sterile variation was found in all rice materials except Nongken 58s, IR24, Zhenshan 97A and Taiyin 1 in R1 generation. Dedifferentiation of explants was essential to producing male_sterile variation, and 2,4-D played a decisive role in this course. The frequency of male_sterile variation in somaclones was affected by the duration of subculture passage. The frequency of male_sterile variation in R2 generat ion (around 2%) was higher than that in R1 generation (around 1%). The higher frequency of male-sterile variation in R2 generation showed that the mutant frequency of one site of a pair of genes from the wild type was much higher than that in a homozygous mutant(two sites of a pair of genes undertaking mutant at the same time).