A benign course of cytomegalovirus (CMV) retinitis is reported in a young patient with selective immunoglobulin G2 (IgG2) deficiency, after corticosteroid treatment for inflammatory pulmonary disease. IgG2 deficiency is a specific disorder of humoral immunity and has little to do with defense against viruses. This case suggests that CMV retinitis can occur in patients with IgG2 deficiency, who have received steroids in a presumedly nonimmunosuppressive dose for associated respiratory disease.