In our prospective controlled study, a total of 185 patients with polymyalgia rheumatica (PMR) and temporal arteritis (TA) diagnosed during 1978-83 and their 925 matched controls were cross checked with the data files at the Cancer Registry of Norway at the end of 1987. Malignancy was registered in 27 patients (14.6%) and 131 controls (14.2%) between 1953 and the end of 1987. Malignancy was registered in 16 (24.6%) of the patients with biopsy demonstrating arteritis temporalis. The hazard rate for developing malignancy after diagnosis for the whole patient population was not significantly different from the controls. The hazard rate for developing malignancy in patients with positive biopsy, however, was 2.35 times higher than in the controls (p = 0.036) and 4.40 times higher than the rest of the patient population (p = 0.007) (Cox proportional hazards model). The general long interval between diagnosis of PMR and/or TA and registration of malignancy (mean 6.5 years) is not consistent with a paraneoplastic mechanism.