Medicinal plants have been historically used as treatment for different kinds of human diseases. In this study, hot water (HW) extract of five Taiwanese traditionally used medicinal plants was evaluated for their in vitro anti-leukemic (including anti-K562, L1210, P3HR1, Raji and U937 leukemia cells) and antiviral (including HSV-1 and HSV-2) activities. Results showed that Blumea lacera exhibited broad anti-leukemic activity at magnitudes ranging from moderate to mild and Ixeris chinensis is effective at inhibiting the proliferation of K562 cells. B. lacera and Tithonia diversifolia suppressed the replication of HSV-1 and HSV-2, and had IC50 values below 100 microg/ml. The medicinal plants showed no cytotoxic effect at concentrations that inhibited HSV infection. It was, therefore, concluded that the HW extract of tested medicinal plants exhibited anti-leukemic and antiviral activities at different magnitudes of potency.