A 34-year-old woman had wide-spread panniculitis due to a disseminated infection with Mycobacteria avium-intracellulare. The patient had previously received treatment with high dosages of corticosteroids. Suppurative lesions teeming with acid-fast bacilli and without formation of granulomas were found in many organs, including the skin, mediastinum, spleen, liver, and gastrointestinal tract. Both the appearance of disseminated M avium-intracellular infection resembling panniculitis and the involvement of mediastinum have not previously been reported, to our knowledge.