Nine potato cultivars (genotypes) were grown under three different locations, Alexandria governorate, Egypt during the summer seasons of 2011and 2012 to determine some genetically parameters affecting potato breeding programs. Phenotypic (p) and genotypic (g) variability and their respective coefficient of variations, genetic advance, and broad-sense heritability, correlation coefficients among all pairs of some important potato characters along with direct and indirect effects of some traits on potato yield trait were studied .The obtained results showed that all the morphological, yield and yield component characters showed highly affecting with the genotype by environment interaction (G X E). The genotypic and phenotypic coefficients of variations had nearly equal values for the characters tuber dry matter, tuber specific gravity and tuber shape index. This result appeared that these traits were not seriously affected by the changes in the environmental factors, indicating a highly significant effect of genotype on phenotypic expression and thus would reflect positive effects for selection during the cycles of the breeding program. The characters plant length (cm), total yield (ton/fed.), No. of tubers/plant, marketable yield (%) and reducing sugars (%) possessed moderate heritability values. Accordingly, it might be stated that phenotypic selection for these characters would be reasonably effective. High heritability value along with high genetic advance as per cent of the mean was obtained for average tuber weight (gm) and tuber shape index traits. Hence, selection for the previous characters would prove quite effective since the characters seemed to be governed by additive genes action.  Tuber yield (ton/fed.) showed highly positive correlation with each of the characters plant length (cm), foliage fresh weight (gm), No. of tubers/plant, average tuber weight (gm) and marketable yield (%). No. of tubers/plant and average tuber weight traits showed positive direct effects on the total tubers yield per feddan. Plant length (cm) and marketable yield (%) characters have indirect positive effects on total tuber yield per feddan through its positive relations with both No. of tubers per plant and average tuber weight (gm).