Background. Interleukin 12R beta 1 (IL-12R beta 1)-deficient patients are prone to clinical disease caused by mycobacteria, Salmonella, and other intramacrophagic pathogens, probably because of impaired interleukin 12-dependent interferon gamma production. About 25% of patients also display mucocutaneous candidiasis, probably owing to impaired interleukin 23-dependent interleukin 17 immunity. The clinical features and outcome of candidiasis in these patients have not been described before, to our knowledge. We report here the clinical signs of candidiasis in 35 patients with IL-12R beta 1 deficiency.