Potato (Solanum tuberosum L.) is the second vegetable crop in Egypt after tomato. Incidence percentage of stem canker and black scurf diseases of potato were monitored 2005/2006 and 2006/2007 in different locations at Behera, Dakahlia, Gharbia, Menofia and Sharkia Governorates. The two diseases were found in all examined locations. The highest percentage of infection was recorded at Sharkia Governorate during the two seasons of summer and winter. Three hundreds isolates of Rhizoctonia solani were obtained from the infected samples. These isolates were identified by classic method, and all isolates were determined as AG-3 by using the different AG- testers. Pathogenicity tests of selected 20 R.solani isolates, according to difference in morphological characters of colony, were evaluated on potato (cv. Monalisa) plants under greenhouse conditions. The highest percentages of stem canker and black scurf were obtained by two Sharkia's isolates (code 18 and 17). Genetic variability among 20 isolates of R.solani was determined using RAPD-PCR technique. The banding patterns generated from those isolates by five primers showed high levels of genetic similarity among the isolates from different geographical locations where the genetic similarity was more than 90%.This technique showed that there was no relation between the geographical locations and genetic content of the tested isolates.