We have shown that human macrophages (m phi s) play an important role in the elaboration of chemotactic cytokines in rheumatoid arthritis (RA) (Koch, A. E., S. L. Kunkel, J. C. Burrows, H. L. Evanoff, G. K. Haines, R. M. Pope, and R. M. Strieter. 1991. J. Immunol. 147:2187; Koch, A. E., S. L. Kunkel, L. A. Harlow, B. Johnson, H. L. Evanoff, G. K. Haines, M. D. Burdick, R. M. Pope, and R. M. Strieter. 1992. J. Clin. Invest. 90:772; Koch, A. E., P. J. Polverini, S. L. Kunkel, L. A. Harlow, L. A. DiPietro, V. M. Elner, S. G. Elner, and R. M. Strieter. 1992. Science (Wash. DC). 258:1798). Recently, m phi inflammatory protein-1 (MIP-1 alpha), a cytokine with chemotactic activity for m phi s and neutrophils (PMNs), has been described. We have examined the production of MIP-1 alpha using sera, synovial fluid (SF), and synovial tissue (ST) from 63 arthritic patients. MIP-1 alpha was higher in RA SF (mean, 29 +/- 8 ng/ml [SE]) compared with other forms of arthritis (2.8 +/- 1.7), or osteoarthritis (0.7 +/- 0.4; P < 0.05). RA SF MIP-1 alpha was greater than that found in either RA or normal peripheral blood (PB) (P < 0.05). Anti-MIP-1 alpha neutralized 36 +/- 3% (mean +/- SE) of the chemotactic activity for m phi s, but not PMNs, found in RA SFs. RA SF and PB mononuclear cells produced antigenic MIP-1 alpha. Mononuclear cell MIP-1 alpha production was augmented with phytohemagglutinin or LPS. Isolated RA ST fibroblast production of antigenic MIP-1 alpha was augmented upon incubation of cells with LPS, and to a lesser extent with tumor necrosis factor-alpha. Isolated RA ST m phi s expressed constitutive MIP-1 alpha mRNA and antigenic MIP-1 alpha. Using ST immunohistochemistry, MIP-1 alpha+ cells from RA compared with normal were predominantly m phi s and lining cells (P < 0.05). These results suggest that MIP-1 alpha plays a role in the selective recruitment of m phi s in synovial inflammation associated with RA.