Primary hyperparathyroidism has been increasingly diagnosed among whites since the advent of the biochemical autoanalyzer. However, the condition remains uncommon among Orientals. Our experience with 31 patients at the Queen Mary Hospital, University of Hong Kong, in the periods before and after we began to use the biochemical autoanalyzer was reviewed. The prevalence of primary hyperparathyroidism rose slightly from 3.1 to 3.7 per 100,000 hospital population. In both periods skeletal manifestation was the major clinical presentation, followed by hypercalcemic symptoms and urologic disease. Asymptomatic hypercalcemia occurred in three of 31 patients despite the use of the biochemical autoanalyzer. Preoperative localization was carried out in 27 patients and was helpful in nine (33.3%) of them. The surgeon explored all four parathyroids, removed the diseased gland(s), and examined a biopsy specimen of one normal-appearing gland. There were 27 adenomas, two carcinomas, one four-gland hyperplasia, and one sarcoidosis. Twenty-eight patients had transient hypocalcemia after parathyroidectomy and required calcium supplements for variable periods. Before and after we began to use the biochemical autoanalyzer, there was minimal change in the prevalence and clinical pattern of primary hyperparathyroidism seen in our hospital. In our experience, successful parathyroidectomy depends more on the surgeon's operative technique than on preoperative localization.