The first known cases of trisomy-3, trisomy-4, and triploidy (3A-ZZZW) in chickens are reported. The trisomic embryos were near death at 4 days of incubation; the triploid embryo appeared normal and probably could have developed further. Although the triploid (3A-ZZZW) was found after sampling more than 2000 embryos, the trisomic-3 and trisomic-4 embryos were discovered in the first sampling of a line of chickens selected for low egg production. These studies suggest that the sex chromosomes (Z and W), as well as the autosomes, can undergo nondisjunction in meiosis of chickens.