CY (Extract of Paeonia lactiflora Pall. ) was found to have significant therapeutic effect ou skin lesions of HSY-1 infection in guinea pigs at 5mg/ml concentration. Inhibition effet on the development of skin lesions was similar to ribavirin, with recoyery 4 days after treatment. At 10 or 2.5mg/ml recovcry was also achieved after 6 or 7 days respectively. The results showed that CY is an effective anti-HSV-1 drug.