BACKGROUND: Previous studies have suggested that infections are an important cause of death in patients with Addison’s disease, but epidemiological studies on the frequency of infections in this population are lacking. OBJECTIVE: To assess and compre the incidence risk of infections in patients with primary adrenal insufficiency with controls. DESIGN AND SETTING: We conducted a cohort study, using data from the Dutch PHARMO record linkage system, that links patients’ demographics and medication histories to hospital admissions. PATIENTS: From a cohort of oral glucocorticoid users, 390 patients with primary adrenal insufficiency were identified by assessing concurrent use of glucocorticoids and mineralocorticoids using pharmacy dispensing records.A reference cohort (n=1933) with the same age and sex distribution was sampled from patients not using glucocorticoids. OUTCOME MEASURE: Incidence rates and incidence rate ratios (IRR) were calculated of infections, defined by use of antimicrobial agents, as well as hospital admissions for infection. RESULTS: The incidence of infectious episodes, defined by usage of antimicrobial agents, among patients with primary adrenal insufficiency (incidence rate 59.2/100 person-years) was 1.5 times higher compared with controls, yielding a crude IRR OF 1.61 (95% CI 1.51-1.72). The IRR decreased slightly to 1.58 (95% CI 1.47-1.70) After adjustment for co-medication and co-morbidity also associated with infection risk. Also with respect to hospital admissions forinfection, the incidence rates observed for patients with primary adrenal insufficiency was higher compared with controls (3.8/100 vs 0.8/100 person-years): crude IRR 5.02 (3.66-6.87) and adjusted IRR 4.34 (95% CI 3.04-6.22). CONCLUSION: Patients with primary adrenal insufficiency had an increased use of antimicrobial agents and hospital admissions related to infection.