Hu, C., Tsao, R., Liu, R., Sullivan, J. A. and McDonald, M. R. 2012. Influence of cultivar and year on phytochemical and antioxidant activity of potato (Solanum tuberosum L.) in Ontario. Can. J. Plant Sci. 92: 485–493. Phytochemicals in coloured vegetables are responsible not only for the colour, but also for nutritional quality. In this study 11 cultivars of potato, with a wide range of skin and flesh colours, grown over two years were tested for the total phenolic content (TPC), total anthocyanin-content (TAC) and total antioxidant activity (TAA). Results showed significant variations among cultivars for both years. TPC was 1.2–3.6 mg gallic acid equivalent (GAE) g^-1 dry weight (DW) in 2008 and 0.98–2.81 mg GAE g^-1 DW in 2009. Total anthocyanin content was 0.70–1.92 mg cyanidin-3-glucoside equivalent (Cy3g E) in 2008 and 0.05 –1.52 mg Cy3g E g^-1 DW in 2009, respectively. The TAA also varied among different potato cultivars, with values of 12 to 64 and 6.3 to 20 µmol ascorbic acid equivalents (AAE) g^-1 DW in 2008 and 2009, respectively for the FRAP (ferric reducing/antioxidant power) assay, and from 42 to 168 and 75 to 174 µmol trolox equivalents (TE) g^-1 DW in 2008 and 2009 in the ORAC (oxygen radical absorption capacity) assay, respectively. The purple fleshed tubers, such as “Mackintosh Black’, demonstrated the highest antioxidant activities, indicating that anthocyanins are important antioxidants. Our results suggest that purple/red potato cultivars have a greater potential as functional foods for enhanced human health benefits.