OBJECTIVE: Metalloproteinases (MMP) play an important role in the remodelling of the extracellular matrix. However, evidence that they are responsible for tissue damage in pathological situations remains circumstantial. Stromelysin (MMP-3) production is increased in rheumatoid arthritis (RA), and has been proposed as a marker of joint damage. The relevance of serum levels of MMP-3 to erosions in RA was studied. METHODS: Fifty-three patients with active RA of > 5 yr duration and with available X-rays were stratified according to disease duration. Hand X-rays were scored for erosions. Patients were then classified into upper and lower quartiles. Serum MMP-3 levels were compared between these two groups. RESULTS: No significant differences in serum MMP-3 were seen between high and low eroders. A statistically significant correlation was observed between sMMP-3 and erthyrocyte sedimentation rate and C-reactive protein. CONCLUSIONS: Serum MMP-3 is not an independent marker of joint damage, but is correlated with systemic inflammation. Its precise role in joint damage in RA remains to be elucidated.