The modal DNA values of 1465 tumours, together with other factors of possible prognostic importance, were related to the survival of the patients, using regression models (Kay, 1977). For most tumour sites except the testis, the distributions of modal DNA values were bimodal, with peaks at the diploid level and in the triploid-tetraploid range. For all tumour sites except the cervix uteri, patients in the low (near-diploid) range showed better survival; the reverse was true for squamous-cell carcinoma of the cervix uteri. Other variables showed the following effects: for all sites except the testis, younger patients showed a better survival; for the cervix and corpus uteri, breast and ovary, increasing clinical stage was associated with poorer survival. Where evaluated, histological grade appeared to be associated with survival rate, the less well differentiated tumours having a worse prognosis, except for the breast, where the reverse correlation was noted. For carcinoma of the bladder, females and a poorer survival rate than males.