Forty-three cases of adult T-cell leukemia (ATL) admitted to our hospital between 1982 and 1987 were studied. Three of those were found to be complicated with diffuse panbronchiolitis (DPB). The incidence of DPB is considered to be significantly higher in patients with ATL. The three DPB-complicated cases composed one case each of the smoldering, chronic, and acute type of ATL. In each type, DPB preceded overt ATL and Candida albicans was found in sputa following detection for bacteria. The DPB complication apparently worsened the prognosis of the ATL patients. We have discussed a possible relationship between ATL and DPB.