The present work was con-ducted at Agricultural Research Station of Sids during the two seasons, 2008 and 2009. The materials used included the off-type plants derived from the Egyptian cotton variety Giza 80 which cultivated in a large scale of the Middle Egypt to study some of their economic traits and their effects in reducing yield and lint quality of Giza 80.  Giza 80 variety as well as its off-type plants were characterized in the field and in the laboratory, growth habits, fruiting behavior yield and yield components, intensity of fuzz distribution on the seeds and fiber properties. Also, the RAPD technique was used as a tool for setting up a convenient and standard protocol to deter-mine the difference and variation between plants of the variety Giza 80 and its off-type plants. Field characterization of the off-types showed, taller plants, longer leaves, different boll shapes and intensity of fuzz distribution on the seeds as compared to their standard type Giza 80. The results showed that the off-type plants of Giza 80 gave considerably lower values for boll weight, seed cotton yield, lint yield, lint percentage, Pressley index, uniformity ratio and fiber length traits, while they gave higher values for micronaire compared with the normal type of Giza 80. As in results of RAPD analysis, ten primers out of the tested thirteen oligomers succeeded to generate polymorphic DNA. Also, revealed that the total number of polymorphic amplicons was (29). This corresponds to level of polymorphism of (29.3 %). There were some specific markers at the molecular level, which could differential between Giza 80 cultivar and its off-types. These results showed differences in size and number of the amplified fragments per primer, indicating a high degree of variability between them. Based on the obtained data of PCR products and a phylogenetic tree, i.e. dendro-gram was constructed for Giza 80 and its off-types. There are some degree of the genetic divergences between Giza 80 cultivar and its three off-types, Giza 80 T1, Giza 80 T2 and Giza 80 T3 which were 20.3 %, 29.2 % and 29.9 %, re-spectively.