The segregation products in zygotes of females heterozygous for the mouse Rb(6.16) translocation were studied. Of 191 first-cleavage metaphase zygotes recovered from 16 females mated to chromosomally normal males, 132 were cytogenetically analyzed after sequential G- and C-banding. There were no products of adjacent segregation, since the six chromosomal imbalances were unrelated to the translocation. Alternate segregation was seen in 126 (95.5%) of the zygotes, with 85 being chromosomally normal and 41 carrying the translocation. These results indicate preferential alternate segregation and a significant deviation from the Mendelian 1:1 ratio (P < 0.005) for reciprocal alternate segregants, as seen earlier for males with this translocation. However, the approximately 2:1 ratio for normal-to-balanced segregants in females is lower than the ratios consistently seen for males. This supports the notion that there are different underlying causes of the distortion in the sexes.