We studied the frequencies of red cell enzyme types, AcP, PGM1 and EsD in 213 patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), rheumatic heart disease (RHD), scleroderma (Scl) and psoriatic arthropathy (PsA). The differences in frequency of AcP phenotypes between RA, Scl, and PsA and the Moscow population were significant. In PsA the PGM1 phenotype 1-1 frequency was significantly decreased, while the phenotype 2-1 frequency was significantly increased.