A gradient reversed-phase HPLC method was developed for the simultaneous separation and determination of rosmarinic acid, lithospermic acid B, caffeic acid, and other phenolic compounds. This method showed a satisfactory result. The limits of detection for these phenolic compounds were ≤0.05 mg/L. The developed method was applied to the determination of phenolic compounds in the dried roots of Salvia miltiorrhiza (Danshen) and the transformed cells of S. miltiorrhiza . In the transformed cells, rosmarinic acid was the predominant phenolic compound. Small amounts of lithospermic acid B and caffeic acid were also detected. In the dried roots, in contrast, lithospermic acid B was the main phenolic compound and only a very small amount of rosmarinic acid was found. In addition, danshensu and some unidentified phenolic compounds were also detected from the dried roots. Keywords: Phenolics; rosmarinic acid; lithospermic acid B; caffeic acid; Salvia miltiorrhiza; HPLC