Pancreatitis occurred in 13 (5.6%) of 234 patients (76 men, 158 women; mean age 63 [2-83] years) who were operated on for primary hyperparathyroidism (pHPT) between 1987 and 1992. The pancreatitis patients had a significantly higher median level of parathormone (340 pg/ml), of serum calcium (3.2 mmol/l) and of thyroid weight (1.7 g) than the remaining 221 patients (135 pg/ml; 2.9 mmol/l; 1.0 g, respectively: P < 0.05 for each). In ten patients pHPT had been diagnosed during an attack of pancreatitis: pancreatitis had been the diagnostic clue to pHPT. After conservative treatment of the pancreatitis and parathyroidectomy seven of the ten patients were free of symptoms during the follow-up. In one patient pancreatitis recurred postoperatively and two patients died of the consequences of haemorrhagic necrotizing pancreatitis. Cholelithiasis, as another possible causative factor for pancreatitis, was present in five of the 13 patients (38%). None of the patients was an alcoholic. These data indicate that there is a positive correlation between advanced pHPT and pancreatitis. Pancreatitis may be the expression of much advanced hyperparathyroidism which has been diagnosed too late.