Restriction fragment length polymorphism (RFLP) in the alpha 1-antitrypsin gene region was studied in relation to chronic obstructive airway disease (COAD) and pneumoconiosis. Genomic DNA of 122 studied subjects was digested with Hind III restriction endonuclease and hybridized with the alpha 1-antitrypsin gene probe. In eight patients with COAD an unusual 10-kb restriction fragment was found hybridizing with the probe. Three of 70 patients were homozygotes for this variant allele and 5 were heterozygotes, showing the presence of two fragments, 2.7 kb and 10 kb. The presence of 10-kb restriction fragment seems to be related to the early development of COAD in studied subjects and therefore might be used as a genetic marker of the disease.