To review retrospectively our clinical experience with surgical treatment and follow-up of pituitary adrenocorticotropic hormone (ACTH) microadenomas at Rui Jin Hospital of Shanghai Second Medical University. Eighty-seven patients with ACTH microadenomas underwent surgery via the transsphenoidal approach. Preoperative computed tomography and/or magnetic resonance imaging revealed microadenomas in only 46 patients and was negative in the remaining 41 patients, which were classified as microadenoma grade 0. High-dose dexamethasone (Dx) suppression testing was positive in 86% of patients and low-dose Dx suppression testing was negative in all patients. Histological confirmation of ACTH microadenoma was made in all 87 cases, with a minimum tumour size of only 1 to 2 mm in diameter. The remission rate was 82% for grade I and 92% for grade 0 microadenomas during 2 to 18 years of follow-up. Neuroimaging studies have limited value in diagnosing ACTH grade 0 microadenoma. Clinical manifestation combined with positive Dx suppression testing is decisive in these circumstances. Surgical intervention could achieve a high relief rate for ACTH microadenomas, especially in grade 0 group.