Within a period of fourteen years 531 operations for growth hormone (GH)-secreting adenomas were carried out. In this consecutive series 73% of the 396 patients who underwent primary transsphenoidal surgery achieved basal GH levels below 5 micrograms/l, and 58% also had an adequate suppression following an oral glucose tolerance test (OGTT). Slightly less favourable results were found in patients requiring surgery following an initial therapy. However, 41% of 121 such patients, who had either been operated upon previously or who had received external or internal irradiation, nevertheless achieved basal GH levels below 5 micrograms/l after the surgical reintervention. Normal suppression of serum GH during an OGTT was observed in 23% of these patients. The overall complication rate was low and tumour recurrences were very rare. To facilitate easier tumour removal, octreotide was preoperatively administered in 53 patients undergoing primary surgery of large adenomas. Recurrences were documented in a few exceptional cases. These data support our previous experience that once a normal suppression of growth hormone has been documented following surgery of pituitary adenomas, the long-term outcome is favourable.