Our aim was to identify histologic changes in cervical carcinoma tumor cells due to chemotherapy,by electron microscopic examination. Cisplatin and 5-fluorouracil were used between March 1, 1994 and February 28, 1995 on a total of 16 patients. The treatment schedule consisted of 75 mg/m2 cisplatin via iv with hyperhydration on Day 1, in combination with 1000 mg/m2 5-fluorouracil via continuous iv on Day 1 to 5. The treatment was repeated every 4 weeks with a maxinum of 3 courses. Ultrastructurally, chemotherapy induced apoptosis,indicated by condensation of nucleus and cytoplasm,fragmentation of nuclei, and apoptotic bodies. Due to repeat chemotherapy, increased levels of desmosomes were noted and parts of tumor nests were replaced by mature squamous cells. Tumor nests were reduced in size, mitochondria exhibited swelling, the endoplasmic reticulum was dilated, and infiltration of inflammatory cells increased after chemotherapy. These results suggest that chemotherapy induces apoptosis and injury to the cytoplasm and nuclei of tumor cells. However, the exact selection mechanism of the biochemical pathway of cell death is not fuUy understood. Further study of the molecular biologic actions of cell death after chemotherapy is warranted.