OBJECTIVES: Pituitary apoplexy is a rare clinical syndrome associated with rapid enlargement of a pituitary mass. We report the initial presentation, subsequent course and outcome of an acromegalic patient who developed spontaneous remission following pituitary apoplexy with pathologic findings of tumor infarction. CLINICAL PRESENTATION: A 38 year-old man with typical acromegalic features was referred to our hospital. He had been diabetic and hypertensive. His basal GH and IGF-1 levels were high (80 mu g/L and 747 ng/mL respectively). Sella MRI showed a macroadenoma about 19x20 mm in size. He admitted to emergency department with complains of severe frontal headache accompanied by nausea and vomiting two days after MRI was taken. His neurological examination and visual field test were normal. Emergent MRI of the sella disclosed an enhancing intrasellar mass of 24x23 mm compressing the optic chiasm. The patient underwent transsphenoidal decompression of the lesion. Histological examination revealed an adenomatous tissue showing nonhemorrhagic coagulation necrosis. Before surgery, his GH levels declined to 2.72 mu g/L spontaneously and after surgery he was in remission even leading to a state of growth hormone deficiency. CONCLUSION: When apoplexy occurs in functionning adenomas, it may cause spontaneous remission. However pituitary apoplexy due to tumor infarction is very rare. Various precipitating factors have been reported in 25-30% of pituitary apoplexy patients. Diabetes mellitus and diabetic ketoacidosis are one of these. The presence of contrast media induced endothelial swelling with the result of hypoperfusion and diabetes mellitus associated vasculopathy might be a precipitating factor in this patient.