Immunohistochemical staining of bcl-2 and p53 proteins was compared with thymidine labelling index (TLI) and cell loss factor (O) in lung cancer. Neither bcl-2 nor p53 overexpression was associated with high cell loss but strong bcl-2 staining was associated with higher TLI. Concomitant strong p53 and bcl-2 expression, not the usual inverse relationship, plus high cell-loss factor was present in three neuroendocrine carcinomas. Other factors presumably have a role in controlling cell death in these tumours.