The effect of a mercurial ayurvedic drug (kajyoli), on the concentration of Na+, K+ and Ca2+ in rat liver, kidney and brain, and on the respiratory activity of these tissues is reported. The doses used were 20 mg and 40 mg X day-1 X kg-1 body wt. daily for 30 days, the lower level being equivalent to the human dose. A marked dose-dependent decrease in respiratory activity occurred in the three tissues. The only significant changes seen in the ion concentration were a decrease in Na+ at the higher dose level in the kidney and a dose-dependent decrease in Ca2+ in the liver.