The balance between Bcl-2 and c-Myc and c-Jun seems to be an important determinant of cellular sensitivity to the induction of apoptosis. High expression of Bcl-2 was noticed to be strongly related to low rates of apoptotic cell death. The mean value of the apoptotic index was 45.0% in Bcl-2-negative tumours and 7.5% in Bcl-2-positive tumours. C-Myc and c-Jun accumulation were associated with the absence of Bcl-2 expression and with increased apoptotic activity. The loss of Bd-2 expression was strongly correlated with increased apoptotic cell death. The inverse correlation is between apoptotic and mitotic index. A high mitotic index exists in most patients with a low apoptotic index. Bcl-2, c-Myc and c-Jun does not only take part in cell death, but also in cell division in breast carcinoma cells in which the regulation of cell division and cell death are strictly connected.