Details of meiotic chromosome studies in four human male translocation heterozygotes are given. All are associated with subfertility. One Robertsonian translocation and one reciprocal autosome translocation appear to be associated with increased levels of abortion. Segregation of unbalanced gametic genomes is thought to be the underlying cause of fetal death. Two other reciprocal autosome translocations are associated with gametogenic failure, leading to azospermia in male heterozygotes.