Hassan, H. M., Jiang, Z.-H., Syed, T. A. and Qin, W. 2012. Review: Northern Ontario medicinal plants. Can. J. Plant Sci. 92: 815-828. The majority of scholarly investigations conducted in the 20th century have provided the incentive for establishing plants as sources of diverse phytochemicals. With infectious and cancerous diseases causing millions of mortalities worldwide, and the advent of resistant strains, the discovery of new antimicrobial and anticancer agents is crucial. Hence, included in this review is a novel list of 48 northern Ontario medicinal plants that may be sources of antifungal, antibacterial and/or anticancer phytochemicals. A total of two ferns and allied plants, two sedges and grasses, six trees, four shrubs, one vine and 33 herbs were identified. These plants were accumulated through interviews with native Elders and a survey of ethnobotanical literature on northern Canadian species of medicinal plants. We also present a critical review of their potential constituents, medicinal properties, and analysis of four promising plants (skullcaps, devil's club, St. John's wort and evergreens). Skullcaps and St. John's wort are model plants with documented anticancer, antibacterial and antifungal bioactivities. However, a considerable gap in ethnopharmacological data was found for species of skullcaps (Scutellaria galericulata, S. parvula and S. lateriflora) and St. John's wort (Hypericum mutilum, H. majus, H. canadense) growing in northern Ontario. These findings provide promising incentives in the ethnopharmacological community for medicinal research in this region.