Mitochondrial kinetics during mitosis in Cryptococcus neoformans was examined with ultrathin serial sections using a computer-aided three-dimensional reconstruction technique. The number of mitochondria varied during mitosis: there was an increase in prophase to telophase cells and a decrease in interphase cells. No appreciable differences in the form and number of mitochondria were found between the cells in the logarithmic growth phase and stationary phase. Fluctuations in the ratio of mitochondrial volume/total cytoplasmic volume were minimum during mitosis. However, the ratio was affected by the growth condition of the cells; that is, the ratio in the logarithmic growth cells was significantly higher than that in stationary cells. A giant mitochondrion, which is composed of a coalescence of all the mitochondria in a cell, was not found in this study.