Temporal trends in the incidence of cancer of the renal parenchyma, renal pelvis, ureter, bladder, urethra and Wilm's tumor in the period 1943-88 were described. Log-linear Poisson models were used to estimate the changes over time and the geographical variations. We have found a steep increase in the incidence of pelvis and ureter cancer; and to some extent also for bladder cancer in men. The incidence of cancer of the renal parenchyma has increased more moderately while the rates of Wilm's tumor have been virtually stable throughout the period. These findings suggest that tumors in the urinary system differ with respect to risk factors and should be grouped by their histological origin as well as topographical site.