High-dose chemotherapy (HDC) followed by autologous hematopoietic reconstitution is an experimental treatment option for patients with epithelial ovarian cancer. However, the incidence of occult ovarian tumor cell involvement in autologous bone marrow (BM) or peripheral blood stem cell (PBSC) autografts has not been widely investigated. We used a highly sensitive immunocytochemical (ICC) procedure that detects occult blood-borne tumor micrometastases. We analyzed 24 BM specimens (15 obtained during therapy and 9 harvest samples) and seven PBSC specimens from 22 patients with ovarian cancer. Overall, ICC analysis detected immunostained tumor cells in 10 of 23 evaluable BM specimens (43%) from 9 of 19 patients (47%). One of 9 (11%) harvest samples contained tumor cells. Only one of the 10 ICC-positive BM specimens had tumor cells detected by routine histopathological analysis. ICC-detectable tumor cells were cleared from the marrow of two patients during chemotherapy. None of the seven PBSC specimens contained tumor cells. We conclude that ovarian cancer micrometastases have the potential to contaminate BM, as is also the case in patients with other epithelial malignancies. In the limited number of specimens analyzed, PBSC harvests appeared to provide a less tumor-contaminated source of hematopoietic stem cells for autologous transplantation.