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.