Diluted Dead-Sea brine and solutions of certain of its salts (chlorides and bromides of Na, K and Mg) were found to reversibly inhibit cell proliferation in culture. Bromides were more powerful as inhibitors than their chloride counterparts, and K salts were more effective than those of Na and Mg. KBr had the strongest inhibitory effect, which equalled that of diluted Dead-Sea brine at the same concentration. The favourable results of the Dead-Sea Spa treatment of psoriasis may thus be partly due to the penetration of minerals into the body, via the skin, with subsequent reinforcement of anti-proliferative mechanisms.