Abstract Accurately diagnosing adrenal insufficiency (AI) is of vital importance, but it can be challenging, particularly in children. While the ACTH stimulation test remains the gold standard test for diagnosing AI, its protocols and interpretation of results remain controversial. There are no international recommendations specific for the pediatric age group. Objective to understand current practices of North American pediatric endocrinologists, regarding the diagnosis of AI in children, with focus in interpreting results of ACTH stimulation tests. Methods an anonymous, electronic survey was sent to members of the Pediatric Endocrine Society in February of 2022. Email reminders were sent over the following month, and the survey was closed after 6 weeks. RedCap was used to administer the survey and store data. Results 221 survey responses were included. 52% of participants had more than 10 years of clinical experience, and 78% practiced in academic centers. All respondents ordered ACTH stimulation tests for the diagnosis of AI; 82% also used morning cortisol levels, 77% used cortisol levels during stress, and 14% used random cortisol. For the diagnosis of primary AI, 85% chose high-dose ACTH stimulation tests (HDST). For secondary AI, 62% ordered low-dose ACTH stimulation tests (LDST), 22% HDST, and the remainder used both. The most frequently used time points for the HDST were 0 and 60 minutes, and for the LDST, 0, 30 and 60 minutes. For interpretation of ACTH stimulation test results, 95% considered peak cortisol levels, 70% also took into context the clinical picture, and 48% considered the relative increase in cortisol levels from baseline. 17% of respondents used different cutoff values for LDST vs. HDST; 18% used specific cutoffs for newborns. Median (IQR) cortisol levels after ACTH stimulation tests for diagnosing AI was 18 (15.5-18) ug/L; 54% of participants used 18 ug/dL, 40% considered levels between 10 and 18 ug/L, and 7% used cutoffs between 18 and 20 ug/L. Finally, 43% of providers did not know what type of cortisol assay was used in their laboratory. Discussion In North America, pediatric endocrinology providers use ACTH stimulation protocols variably, including decisions about HDST vs. LDST, time points for cortisol measurement, and interpretation of results. Notably, there was a wide distribution of responses concerning cortisol cutoffs. Also, a significant proportion of providers who ordered and interpreted results of ACTH stimulation tests did not know which biochemical assay was employed. These exploratory results highlight the need for pediatric-specific recommendations on ACTH stimulation protocols, based on the best available evidence. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.