The authors review the epidemiology, clinical manifestations, diagnosis and treatment of Pneumocystis jiroveci thyroiditis of 15 cases reported in the medical literature. Patients with acquired immunodeficiency disease syndrome were particularly at risk. P. jiroveci thyroiditis was diagnosed at autopsy as a part of disseminated infection in a substantial number of patients without clinical manifestations and laboratory evidence of thyroid dysfunction. Local signs and symptoms of infection were indistinguishable from other infectious thyroiditis and included neck enlargement with or without cervical pain, sometimes associated with dysphagia and dysphonia, and clinical and laboratory features of hypothyroidism. Antemortem diagnosis of fungal thyroiditis was made by direct microscopy and culture of a fine-needle aspirate in most cases. As most patients with P. jiroveci thyroiditis had disseminated Pneumocystis infection with a delay in diagnosis and treatment, the overall mortality was high. Pneumocystis jiroveci thyroiditis is rare but should be suspected in HIV-infected patients with CD4 count lower than 200 cells micro(-1) on prophylatic inhalatory pentamidine who present with neck enlargement with or without pain, and clinical and laboratory evidence of hypothyroidism.