During an in-vitro fertilization programme, 320 inseminated oocytes neither formation of pronucle nor cell cleavage were studied Cytogentically. Fourteen of 17 oocytes exhibiting no extruction of polar were characterized by an approximately diploid set of metaphase II chromosomes with four of these oocytes also showing an additional set of prematurely condensed sperm chromosomes of the G₁ phase (G₁ -PCC). These chromosomes were single chomatids. Among 211 occytes characterized by polar body extrusion, the same type of chromosomes were found in 22, along with metaphase II chromosomes in the haploid range. This phenomenon can be explained by the permanent arrest of the oocytes at metaphase II after sperm penetration, which allows the presence of the permanent arrest of the oocytes at metaphase II after sperm penetration, which allows the presence of cytoplasmic chromosome condensing factors to remain, leading to the induction of PCC in the sperm. In these cases, PCC resulted either from distinct pronuclear asnchtrony or interchromosomal asynchrony within the chromosome set.