Idiopathic pulmonary fibrosis (IPF) risk-related factors were epidemiologically investigated on the basis of 1,311 Japanese IPF autopsy cases selected from the annual complications of autopsy data records in Japan during a 12-yr period. Age and sex distribution of the subjects revealed a high peak in their seventh decade with males predominating. The IPF rate was more than two times higher (p < 0.01) among subjects engaged in occupations that exposed them to dust or organic solvents compared with those in other jobs. To ascertain job characteristics, an autopsy-case control study was conducted using other annual volumes of the autopsy data records and a similar tendency was observed. Then, a live-case control study was undertaken of 86 subjects with IPF. A significantly higher odds ratio was noted among metal production workers and miners compared with healthy and hospital control subjects (1.37 and 1.34, respectively, p < 0.01), and also a significantly lower odds ratio among subjects who frequently eat fish. Taken together with results of recent in vitro studies, the intrapulmonary deposition of hazardous dusts, especially metallic dusts, appears to play at least a partial role in initiating IPF.