ObjectiveTo explore the value of bilateral inferior petrosal sinus sampling (BIPSS) for preoperative diagnosis of adrenocorticotropic hormone (ACTH) microadenomas.MethodsWe retrospectively analyzed the clinical date of patients with ACTH microadenomas, who were experienced BIPSS preoperatively from October 2013 to May 2017. The qualitative and localized diagnostic significance of BIPSS was evaluated based on the criteria of the plasma ACTH concentration ratio of inferior petrosal sinus to ulnar vein (≥2), and the ratio of left to right inferior petrosal sinuses (≥1.4).ResultsFive patients (1 male and 4 females) were involved in the study. The mean age was (49.6±9.2) years, and the mean disease course was (17.2±7.5) months. The plasma ACTH concentration of all the cases ran up to the criterition of the ratio of inferior petrosal sinus to ulnar vein (≥2). Three cases were found that the actual locations of the microadenomas were inconsistent with the indications from the results of BIPSS. After the BIPSS procedure, there was no intracranial infection or death case, except that one patient suffered from ecchymoma and another one suffered from transient nausea.ConclusionBIPSS is valuable for qualitative diagnosis, but not effective for localization diagnosis of the ACTH microadenomas preoperatively.