Abstract: Objective Primary adrenal insufficiency (PAI) is a rare disease with an increasing prevalence, which may be complicated by life-threatening adrenal crisis (AC). Good quality epidemiological data remain scarce. We performed a Belgian survey to describe the aetiology, clinical characteristics, treatment regimens, comorbidities and frequency of AC in PAI. Methods A nationwide multicentre study involving 10 major university hospitals in Belgium collected data from adult patients with known PAI. Results Two hundred patients were included in this survey. The median age at diagnosis was 38 years (IQR 25–48) with a higher female prevalence (F/M sex ratio = 1.53). The median disease duration was 13 years (IQR 7–25). Autoimmune disease was the most common aetiology (62.5%) followed by bilateral adrenalectomy (23.5%) and genetic variations (8.5%). The majority (96%) of patients were treated with hydrocortisone at a mean daily dose of 24.5 ± 7.0 mg, whereas 87.5% of patients also received fludrocortisone. About one-third of patients experienced one or more AC over the follow-up period, giving an incidence of 3.2 crises per 100 patient-years. There was no association between the incidence of AC and the maintenance dose of hydrocortisone. As high as 27.5% of patients were hypertensive, 17.5% had diabetes and 17.5% had a diagnosis of osteoporosis. Conclusion This study provides the first information on the management of PAI in large clinical centres in Belgium, showing an increased frequency of postsurgical PAI, a nearly normal prevalence of several comorbidities and an overall good quality of care with a low incidence of adrenal crises, compared with data from other registries.