It is now recognized that apoptosis plays an important role in the pathogenesis of tumors. This study evaluated the extent of apoptosis in different grades of ovarian tumors and correlated it with the expression of apoptosis regulatory genes, p53 and bcl-2 and with the total proliferative compartment of the tumor defined by the expression of the proliferating cell nuclear antigen (PCNA). Apoptosis was evaluated by the TUNEL (Tdt-mediated dUTP biotin nick end labelling) assay. Expressions of p53, bcl-2 and PCNA were analyzed by immunohistochemistry. A negative correlation was observed between the expression of bcl-2 and the extent of apoptosis (r = -0.3336, p = 0.019). P53 accumulation directly correlated with the extent of apoptosis (r = 0.485, p = 0.00041). The labelling index of PCNA also showed correlation with expression of p53 (r = 0.49, p = 0.00000). Apoptosis was significantly higher in poorly differentiated tumors when compared to the well- and moderately-differentiated tumors (r = 0.49152, p = 0.00034). Such poorly-differentiated tumors also showed high p53 overexpression and loss of bcl-2 expression. The present study thus provides evidence that dysregulation of apoptosis and its regulatory genes is associated with increasing malignant potential and may thus contribute to the pathogenesis of ovarian tumors.