Four new oxazole-containing diterpenoids, salvianans A-D (1-4), along with three known diterpenoids (5-7), were isolated from Salvia miltiorrhiza cell cultures. The structures of the new compounds were elucidated using spectroscopic methods and single-crystal X-ray diffraction. The evaluation for their anti-HIV-1 activities revealed that 2 and 3 displayed inhibitory activities with IC50 values of 0.03 and 1.2 muM, respectively. The time of addition (TOA) assay and long terminal repeat (LTR) luciferase reporter assay results indicated that compound 2 was an HIV-1 transcription inhibitor and might be a lead compound of antiviral agents acting on HIV-1 transcription.