Abstract: Tanshinone is the neutral fraction of an ether extract of Dan-Shen, the root of Salvia miltiorrhiza Bunge. Ten components have been isolated from tanshinone, among which crypototanshinone, dihydrotanshinone Ⅰ, hydroxytanshinone Ⅱ-A, methyl tanshinate and tanshinone Ⅱ-B are bacteriostatic against Staphylococcus aureus. The total tanshinone was studied in the experiments-reported presently.The antimicrobial action of tanshinone was studied in vitro. It exhibited inhibition, against Staphylococcus aureus, especially against drug-resistant strains. It showed inhibition also against H37Rv and two dermatophytes.Tanshinone showed no toxic effects in mice or rats given p.o. or s.c. Antipyretic action was demonstrated in rabbits. While no therapeutic effects of tanshinone could be demonstrated in mice infected i.p. with Staphylococcus aureus, when given orally with the addition of a sub-effective dose of aureomycin, its therapeutic, efficacy became wellshown. Tanshinone was also shown to be anti-inflammatory in rats with in fective arthritis and in mice where inflammation was produced on the ear with croton oil.Tablets and ointmentof tanshinone gave satisfactory clinical results in 455 cases of infection mainly with Staphylococcus aureus; among these some patients had failed to respond favorably to treatment with antibiotics.A discussion on the way of studying the antibacterial action of traditional medicinal herbs is presented.