The frequencies of GC phenotypes in 104 patients with chronic obstructive airways disease (COAD) were compared with those in 413 control subjects. The distributions were significantly different with fewer patients with the GC 2 allele than expected (relative risks = 0.8, 0.7 and 0.5 for 2-2, 2-1S and 2-1F, respectively) and more 1F-1F patients than expected (relative risk = 4.8). These data suggest that the GC 2 allele exerts a protective effect, whereas 1F, when homozygous, increases the risk of developing COAD.