The impact of therapeutic interventions on the disease process in patients with rheumatoid arthritis (RA) is complex. The effect on the acute phase response was studied in 25 in-patients on imposed bed rest, who were randomised to treatment with (n = 12) or without (n = 13) intra-articular steroids. C-reactive protein (CRP), ESR and IgA alpha-1 antitrypsin complex levels were measured on admission and on days 3 and 5. Levels at onset were not different between groups. At day 3 and day 5, a significant (p < 0.001) fall in CRP was seen only in the intra-articular steroid group. Other cytokine and disease parameter measures did not alter during the study period (although IL-6 and CRP correlated at onset in all 25 patients). The mean duration of the hospital stay was longer for the patients treated with bed rest only. Thus, bed rest when combined with intra-articular steroids produced a rapid systemic effect, while bed-rest alone did not have an effect on the acute phase response over this short time scale.