Prognostic factors are needed for the management of patients with adrenocortical tumours. For this reason, the nuclear DNA content of patients with adrenocortical tumours was analysed by flow cytometry. The relationships between nuclear DNA content, histological indices, and clinical parameters were studied. DNA ploidy could be evaluated in 54 carcinoma and 31 adenoma patients. Twenty-one (68%) of the adenomas, and 6 (11%) of the carcinomas, were DNA diploid. Hypo/Hyperdiploidy was found in 5 (16%) of the adenomas, and 15 (28%) of the carcinomas. The remaining patients had a DNA index above 1.40. A shorter survival was found in patients with diploid carcinomas (P < 0.05). A longer disease-free survival was seen in patients with hypo/hyperdiploid carcinomas (P < 0.05). Nuclear DNA content was not related to the histological index, nor to clinical parameters. We conclude that nuclear DNA content is related to (disease-free) survival of patients with adrenocortical carcinomas. An adenoma-carcinoma sequence may be present in the adrenal cortex. In adrenocortical tumours ploidy evolution appears to be different than that observed in other solid tumours.