Abstract: The male gametophyte development in a cytoplasmic male sterile (CMS) line 8A of sweet pepper (Capsicum annuum L.) and its maintainer line 8B were studied by optical and transmission electron microscope.The results showed that microsporogenesis could process normally and there was no difference in the tapetal cell between 8A and 8B lines before tetrad stage.Then, uninucleate pollen of 8A underwent a progressive process of rupture, owing to squeezing by abnormally swelled tapetal cells and to the premature degradation of tapetal cells.Male gametophytes in 8A ruptured before the first mitosis and became sterile.The results from ultrastructure observation revealed the presence of vacuolated mitochondrias in the tapetum of 8A.This suggests that the genetic defects in male-sterility include gross morphological changes in mitochondria and occur on the early stage of anther development.