The Persian walnut (Juglans regia L.) is one of the most important horticultural crops grown in Iran. This research was conducted to determine the variation in walnut germplasm grown in the Arak region of Iran during the 2007-2008 growing seasons. All of the selected genotypes originated from seed, and their phenological and pomological characteristics were evaluated. Results indicated that there were promising genotypes within the walnut populations in the studied region. Genotypes MS26, MS6, MS34, MS45, MS70, MS49 and MS54 were late bearing leaves (21 to 25 April). Genotypes MS27 and MS29 were completely homogamous. Bearing habit was lateral and terminal in 38.57 and 61.43% genotypes, respectively. Genotypes MS8, MS10, MS48 and MS66 were early maturing and their nuts matured before 10 September. High variation for nut and kernel characteristics was found among the studied genotypes. Genotypes MS15, MS17, MS19, MS20, MS23, MS26, MS27 and MS29 were identified as promising, because their kernel weight, nut weight and kernel ratio were higher than 6 g, 12 g and 50%, respectively. These superior genotypes could be used for cultivation or as parents in future breeding programs.