alpha 1 Antitrypsin (PI) phenotypes were defined in 144 patients with rheumatoid arthritis (RA) and in 223 normal controls. The frequencies of the rare F, S, and Z variants were similar in RA and control groups. No relationships were found between PI allotypes and rheumatoid disease severity or autoantibody titre. The PI M1M2 phenotype was increased in frequency in the RA group, and phenotype frequencies in DR4 positive and negative disease were similar. These results support the suggestion that genes on the 14th chromosome which are linked to PI predispose to RA.