Abstract： Objective　To discuss the etiology, diagnosis criteria and treatment of Nelsons syndrome. Methods　23 cases of Nelsons syndrome operated in our department in last 19 years were analyzed retrospectively. The clinical features included increasing cutaneous pigmentation after bilateral adrenalectomy, markedly elevated ACTH level, pituitary adenoma in CT or/and MRI. Transsphenoidal surgery was done in 21 cases, transfrontal craniotomy in 2 cases. A follow-up period ranged from half a year to 9 years. Results　The incidence of Nelsons syndrome was 7.7% in series of 300 patients with Cushings disease treated by surgery in the same period. Hyperpigmentation was relived in all cases and ACTH level decreased. 8 cases with visual disturbance improved after surgery. Curative ratio was 56.5%, remission ratio was 26.1%. Conclusions　Transsphenoidal microsurgical removal of pituitary ACTH adenoma is the first choice in prevention and treatment of Nelsons syndrome. Follow-up examinations should be repeated at intervals.