A total of 16 ethanol extracts of Turkish medicinal plants were evaluated for antiviral activities against herpes simplex virus (HSV) and Sindbis virus (SINV). Extracts of Galanthus elwesii and Rheum ribes showed the most potent anti-HSV activities, while six other extracts had weaker activities. Galanthus elwesii and Leucojum aestivum were the most potent anti-SINV extracts with four others showing weaker activities. In total, five extracts were active against both viruses, three were selective for HSV and one was selective for SINV. Evidence for an antiviral photosensitizer was obtained in two anti-HSV extracts, in which activity was either completely dependent on light, or was considerably enhanced by light. Thus, several Turkish medicinal plants appear to be promising sources of antiviral activities.