Childhood sarcoidosis is a disease with multisystem organ involvement, and initial presentation as fever of unknown origin (FUO) is relatively common. We describe herein three children (aged 9, 7, and 11 years) with sarcoidosis who were seen initially with FUO. Common clinical and laboratory features include fever of > 2 weeks' duration, weight loss, fatigue, leg pain, anemia, increased erythrocyte sedimentation rate, elevated immunoglobulin G level, negative antinuclear antibodies and rheumatoid factor, and negative purified protein derivative and Candida skin tests. Two patients had iridocyclitis, one had hilar adenopathy, and two had angiotensin-converting enzyme serum levels. All three had no evidence of pulmonary infiltrates on chest radiographs. Bone marrow biopsies for all three were normal, and with no evidence of malignancy. Plain radiographs of the lower extremities and bone scan were normal. Magnetic resonance imaging (MRI) of the lower extremities revealed intact bone architecture and multifocal nodular lesions within the marrow. Bone biopsy from the tibia performed on two patients showed normal bone trabeculae and a solitary noncaseating epithelioid cell granuloma. Noncaseating granuloma was found on reevaluation of the bone marrow biopsy in the third patient. All three patients had negative marrow stains and cultures for fungi and mycobacteria. We conclude that MRI was very useful in the diagnosis of sarcoidosis in children with FUO.