Invasive infection with fungi of the Basidiomycota (rusts, smuts, toadstools, mushrooms, and puffballs) is extremely rare. We report such an infection in a patient with human immunodeficiency virus disease who presented with chronic maxillary sinusitis associated with the mushroom Schizophyllum commune. The organism was isolated from the surgical drainage material, and septate hyphae were seen invading the maxillary submucosa. The limited literature on this subject is reviewed.