We studied chemiluminescence (CL) responses and chemotaxis of monocytes of patients with early rheumatoid arthritis (RA) before starting anti-rheumatic drag treatment and correlated the data to 2-year prognosis of the patients. Luminol-enhanced CL responses of RA monocytes to N-formylmethionyl-leucyl-phenylalanine or to phorbol myristate acetate, and lucigenin-enhanced responses to opsonized zymosan particles were significantly higher than those of healthy control subjects. Distances of chemotactic, chemokinetic and random migration of RA monocytes were similar to those of control cells. High CL responsiveness correlated with seropositivity but not with presence of HLA-DR4 or that of erosions at 2-year follow-up. The results give credence to the view that monocytes are metabolically activated in early untreated RA, but increased respiratory burst activity does not predict early development of erosions.