Nine Irishi potato varieties imported from Canada were studied in 14 field trials over a period of years. The results obtained have shown that Green Mountain was the highest yiel-der, but the least resistant to late blight. This variety, as well as Sebago, showed the highest incidence of internal brown spot. All varieties tried were found to be fairly susceptible to early blight, one of the important disease problems of this crop in Sao Paulo. Irish Cobbler gave the best yields under irrigation and on flat low land.