The filamentous basidiomycete Ceriporia lacerata, an agent of white rot on wood, has never been reported in human disease and its clinical significance is not yet known. We describe 4 patients with respiratory diseases where C. lacerata was implicated in a wide spectrum of clinical manifestations ranging from saprobic colonization to fungal pneumonia. The isolates did not show the morphological characteristics that facilitate recognition of filamentous basidiomycetes, such as the presence of clamp connections, spicules along hyphae, or fruiting bodies. The identity of the mold was confirmed by sequencing the internal transcribed spacer 1 and 4 (ITS-1 and ITS-4) and D1/D2 regions of the rRNA gene. All of the isolates exhibited the lowest MICs of posaconazole and isavuconazole (MIC range, 0.06 to 0.125 mug/ml), followed by itraconazole (MIC range, 0.06 to 0.5 mug/ml), voriconazole (MIC range, 0.125 to 0.5 mug/ml), and amphotericin B (MIC range, 0.25 to 1 mug/ml). The infections reported here occurred in patients with preexisting lung damage induced by tuberculosis or chronic obstructive pulmonary disease. Chronic, sometimes fatal infections by the ascomycete Aspergillus fumigatus and the basidiomycete Schizophyllum commune are well established in the presence of an anatomical pulmonary defect or in the background of immunodeficiency. It is postulated that C. lacerata, a novel opportunist basidiomycete, may be involved in similar pathological processes.