Protein was found significantly more frequently in single urine samples from 504 patients with malignancy (290; 58%) than in 529 controls (119; 22%) (p<0001). Median protein concentration was greater (p<0-001) in patients with neoplasia (0-14 g/1) than in controls (0-07 g/1). Actuarial analysis showed a median survival of 4.5 months in patients with proteinuria compared with 10 months in those without (p<0-001). The association between proteinuria and shorter survival was statistically significant for patients with gut tumours, lung tumours, and tumours at other sites analysed as a group. Patients with myeloma or urinary tract tumours were not studied. In many patients with malignancy the presence of proteinuria may be associated with a substantially reduced survival time.