In the present study we wished to determine whether radiosensitisation could be achieved in a range of colorectal adenoma and carcinoma-derived cell lines (with mutant p53), using UCN-01 at non-toxic doses that can be tolerated by animals and humans (Hill et al, 1994; Fuse et al, 1998; Sausville et al, 1998). The gene discussed is TP53; the disease is carcinoma.