The association between diet and the 25-year incidence of chronic nonspecific lung diseases (CNSLD) was studied in 793 middle-aged men in the town of Zutphen, the Netherlands, in 1960-1985. During follow-up, 232 new cases of CNSLD were identified. The incidence rate was 14.1 per 1,000 person-years. Habitual food intake was assessed by the cross-check dietary history method. The intake of linoleic acid was positively associated with the incidence of CNSLD. The relative risk was 1.55 (95% confidence interval (Cl) 1.11-2.16), comparing the highest with the lowest quartile of intake of linoleic acid, independent of potential cofounders (age, cigarette smoking, body mass index, and energy intake). Alcohol consumers showed a significantly lower risk than did non-consumers (relative risk (RR) = 0.72, 95% Cl 0.55-0.95) after adjustment for confounders. In addition, fruit intake was inversely related to incidence of CNSLD (RR = 0.73, 95% Cl 0.53-0.99). No association was observed with intake of several antioxidants. These results suggest that in addition to well-established determinants, such as cigarette smoking and occupational exposure, dietary factors may play a role in the onset of chronic nonspecific lung diseases.