The prognostic/predictive role of both CD133 and Aldehyde dehydrogenase (ALDH) expression in human ovarian cancer remains elusive. This is an observational study that investigated the expression of CD133 and of ALDH enzymatic activity in fresh ovarian cancer samples and their association with different clinic-pathological patient' characteristics and explored their possible predictive/prognostic role. We analyzed the expression of CD133 and ALDH enzymatic activity in 108 human ovarian cancer samples. We found that among the total patients analyzed, 13% of them was completely negative for ALDH activity and 26% was negative for CD133 staining. Both markers were variably expressed within the samples and when both studied in the same tumor sample, no statistically significant correlation between ALDH enzymatic activity and CD133 expression was found. No statistical significant correlation was found also between the percentage values of positive ALDH and CD133 cells and the number of serial passages patient's cultures underwent, suggesting that these markers do not confer by themselves a self-renewal growth advantage to the cultures. Lower levels of CD133 were associated with higher tumor grade. No correlation with response to therapy, progression free survival and overall survival was found. Our data suggest that neither ALDH enzymatic activity nor CD133 expression provide additional predictive/prognostic information in ovarian cancer patients.