Homozygous γTub37C¹², γTub23C^PI females are sterile but lay a few eggs. Their ovaries are reduced in size and contain only a few egg chambers. Some of the ovaries are completely empty or contain only one or two degenerating egg chambers, whereas others contain some egg chambers at various stages of development, including mature oocytes. These phenotypes are rescued by the addition of either γTub37C^+t7.2 or γTub23C^+tLa. In γTub37C¹², γTub23C^PI females there are no significant differences between mutant and control in the average number of ovarioles per ovary. However more than half of the ovarioles are empty, and the average number of egg chambers per ovary in the mutant is about eight times less than in heterozygous flies and about half of them are abnormal. Within the egg chambers that develop, about 50% show abnormalities. Most abnormal egg chambers present one of three major phenotypes: degenerating egg chambers with pycnotic DNA, egg chambers with 14 nurse cells and two oocyte-like nuclei and compound egg chambers that contain >16 cells. the remaining abnormal egg chambers show a variety of phenotypes, which occur at a lower frequency. These include egg chambers with <16 germ cells, egg chambers with misplaced oocyte or abnormally shaped oocyte nucleus, oocytes containing endoreplicated nuclei, reduced oocyte growth, abnormal positioning of the dorsal appendages, and egg chambers containing 16 nurse cells and no oocyte. Egg chambers that contain too many germ cells are of two types in γTub23C^PI, γTub37C¹² mutants. In egg chambers which contain two distinct groups of nurse cell nuclei of different dimensions and two oocyte nuclei, the cause for the supernumerary germ cells was fusion. Consistently, in these egg chambers there are two distinct populations of ring canals and four ring canals by each oocyte. Two clearly distinct microtubule foci can be seen, each associated with one oocyte nucleus. In contrast, in egg chambers where the dimensions of most nurse cell nuclei and ring canals are mixed and heterogeneous, the supernumerary cells are probably produced by extra rounds of mitosis. At a low rate, egg chambers with too few germ cells are also observed in these ovaries and are in part produced by abnormal migration of the follicle cells within a forming egg chamber. A high percentage of the abnormal egg chambers found in γTub37C¹², γTub23C^PI double mutant females contain 14 nurse cell nuclei and two oocyte-like nuclei. In these cases, one of the two oocyte-like nuclei is always located posteriorly and within one of the four ring-canal cells of the cyst, like a wild-type oocyte. The second oocyte-like nucleus, on the other hand, can be found anywhere within the egg chamber, in cells with any number of ring canals. Thus, the ectopic oocyte-like nucleus does not belong to the second pro-oocyte. The level of endoreduplication of the ectopic oocyte-like nucleus is variable. The 14 + 2 egg chamber phenotype was never observed after stage 10.