Abstract Gans et al. (1975) isolated female-sterile mutants, viable and normal in the homozygous state, producing apparently normal eggs which were unable to develop or developed into defective embryos or adults, even when fertilized with wild-type sperm. Developmental abnormalities of these mutants were surveyed by observing living and fixed material. The following types of mutants were distinguished according to the predominant developmental defect: (i) Eggs not developing at all, mostly remaining unfertilized. (ii) Eggs stopping development after a few cleavages, some with polyploid nuclei. (iii) Eggs stopping development at various embryonic stages, with haploid nuclei. (iv) Eggs with abnormal blastoderm, not developing further or giving abnormal embryos. (v) Eggs with abnormal gastrula, in one case with excessive invaginations, in another case with germ band failing to elongate. (vi) Eggs with embryos dying at different stages, without easily visible effects. Several of the mutants were temperature sensitive. In all the mutants there were eggs that died without developing. Most of the developmental defects appear to be due to general metabolic disturbances of the egg, not directly related to morphogenesis. There were no mutants affecting determination of a particular adult organ. The closest to a morphological type of mutation were those with abnormal blastoderm having successive bands of nuclei of different sizes. Those mutants were thermosensitive; at permissive termperatures they developed into agametic adults or adults with various defects of abdomens, wings or eyes. The nature of maternal genetic control of early morphogensis was discussed.