Summary The histamine H2-receptor antagonists burimamide and cimetidine cause inhibition of human skin histamine-N-methyl transferase (HMT) in the dose range 10-3–10-4 M. Amodiaquin, a recognized inhibitor of animal HMT, also produced dose-related inhibition of human HMT. These findings may explain the observation that H2-receptor antagonists enhance certain types of inflammatory response in skin.