GH and IGF-I levels are elevated in patients with acromegaly. At the time of diagnosis patients present with macroadenomas with a high surgical failure rate or microadenomas. Administration of octreotide (100 micrograms, three times daily) suppressed GH secretion during 8 h to < 5 micrograms/l in 47% and to < 2 micrograms/l in 26% of acromegalic patients after two weeks. IGF-I levels were normalized in up to 70% of patients. Increasing the dose of octreotide to 250 micrograms three times daily did not further improve results. Tumour shrinkage occurred in 37% after six months of treatment, while symptoms improved in 70%. Transient diarrhoea and nausea were noted in 88%, but after six months only 10% reported these symptoms. Gallbladder sludge and gallstones were noted in 19% of patients. IGF-I levels were normalized in 82% of patients with microadenoma and in 50% with macroadenoma. Well-defined pituitary adenomas are usually surgically removed. Invasive tumours are difficult to remove surgically but preoperative octreotide may shrink adenomas and improve response. Octreotide therapy, unlike surgery and irradiation, does not compromise pituitary function. This study suggests that octreotide therapy could be a viable primary management of small discreet adenomas. Where surgery and octreotide fail, other treatments of adenoma include bromocriptine and radiotherapy.