Yield and fiber quality characteristics are among the basic goals that the breeder seeks to maintain. The uniformity and homogeneity of these characteristics represents the practical criteria for identification and judging the purity of the cotton varieties. Maintaining genetic purity among cotton genotypes provides some protection against declining of yield potentials. The spontaneous genetic changes were assessed among Giza 86 and Giza 94 standard cotton cultivars and their off types at Sakha Agric. Res. Stat. - Kafr EL Sheikh, Agric. Res. Center, Egypt, during 2021-2023. Significant differences were observed between the original parents either Giza 86 or Giza 94 and their derived off types as a result of significant differences among original parents vs. off types. The off types showed inferior values in most yield and fiber traits, decreased in lint percentage, fiber length with coarser and weaker lint and changed in lint color, light, radish to dark creamy lint. The differences among the standard cultivars Giza 86, Giza 94 and their off types were mainly affected by two factors, the first factor was due to the cultivars and their off types, and the second factor was concerning the ability of characters that might exhibit discrimination. While, ISSR primers flanked 68 loci in Giza 86 and their off types with an average 9.71 bands per primer and 61.76 % Polymorphism. While, the most important difference revealed SSR primers was a repeat of the band within the genotypes.