The effective thermal conductivities of potato were measured at various stages of the frying process. Samples were taken at 30 s intervals during frying, and two different methods (line heat source and modified Fitch method) were used to measure the effective thermal conductivity. An iterative Kopelman model was used for the prediction of thermal properties. The effective thermal conductivity decreased as frying time increased. The variation of experimental measurements by both methods and modeling were within 10% over most of the range studied. The probe method yielded values that were not significantly different than the modified Fitch method. Lower standard deviations were obtained with the modified Fitch method.