Serum interleukin 6 (IL-6) was measured in patients with pustulosis palmaris et plantaris by a fluorescent sandwich enzyme-linked immunosorbent assay (ELISA) method. Increased production of IL-6 was observed in 8 cases out of 10 showing numerous pustules in their active stage. Six cases were measured before and after tonsillectomy, and statistically significant reduction in the levels of IL-6 paralleled an improvement in the disease activity. It is suggested that IL-6 may be one of the mediators which link tonsillectomy to the activity of pustulosis palmaris et plantaris.