The susceptibility of 21 potato cultivars to leak (watery wound rot) caused by Pythium aphanidermatum was compared. Whole tubers were inoculated after wounding by dipping into a water suspension of 103 oospores/ml and incubated for 3 days at 25 °C. The mean penetration of tissue calculated from the recording of lesion width and depth and the qualitative assessment of rot extension were highly correlated. For 10 of 12 cultivars tested at least twice, consistent reactions were obtained: cvs Korrigane, Superstar, Safrane and Yesmina were moderately susceptible, whereas Atlas, Diamant, Mondial, Obelix, Spunta and Timate were susceptible to highly susceptible. Tubers originated from two locations and/or two cropping seasons; thus, the performance of these cultivars under different production conditions reveals a satisfactory level of agreement with the test. Moreover, ratings assigned are supported by field or store observations.