The total polyphenol (TP) content in and antioxidant activity of potato tubers of four yellow-fleshed varieties and two purple-fleshed varieties from the 2004 harvest were assayed. The TP content was determined with the Folin-Ciocalteau reagent and antioxidant antiradical activity by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. Significant differences in the TP content between the groups of yellow-fleshed varieties were found. Significant differences between yellow and purple-fleshed potatoes were also found in antioxidant activity both between yellow and purple-fleshed varieties and within purple-fleshed varieties. The higher potatoes-growing regions showed an apparent tendency to higher TP contents in analyzed varieties. In some varieties the effect of four variants of growing was assayed and a significant effect of high potassium doses (200 and 130 kg K₂O per hectare) on the decrease in TP was estimated.