We report the stimulation of elastase activity of human skin fibroblasts by interleukin-1 beta (IL-1). Elastase activity was determined by the hydrolysis of the synthetic substrate succinoyl trialanine paranitroanilide (Suc(Ala3)NA). Recombinant human IL-1 beta induced a concentration-dependent increase in the elastase activity of fibroblasts. The supernatants of keratinocyte cultures that contained IL-1/ETAF showed similar stimulatory activity.