Of 263 oocytes that failed to fertilize after in-vitro fertilization and were sent for cytogenetic investigation, 179 (68.1%) were analysable. More than 72.0% were normal metaphase II haploids (23,X). Hyperhaploidy, hypohaploidy and complex cases made up a total aneuploidy rate of 12.3%, while 10.1% were diploid. In addition, there were five oocytes with structural aberrations and eight yielded chromatids only. The total chromosome aberration rate was 29.1%. No significant difference was found between the aneuploidy rate and maternal age. Here we present photographic evidence of oocytes with extra whole chromosomes and extra single chromatids. We suggest that both predivision and nondisjunction contribute to the formation of trisomy in man.