The expression of seed characteristics would facilitate further improvement of cotton seed properties in breeding programme. Thus, this research aimed to estimate genotypic and phenotypic coefficients of variation, heritability, correlation coefficient and genetic diversity of extra long stable Egyptian cotton genotypes. All genotypes were grown at two locations, El-Behera and Domietta govemorates during 2002 and 2003 seasons. The results revealed that the differences among the genotypes were highly significant for all studied traits. Significant interactions between genotypes and locations were found for most studied characters. Highly significant positive correlations were recorded between both seed cotton yield and embryo index, seed index, . seed density, seed protein %, seed protein index and seed oil index. Also, significant positive correlation between seed cotton yield with germination %, embryo % and seed oil %, while significant negative correlation was obtained with earliness % and seed coat %. Significant positive correlations between chemical seed qualities, seed oil %, seed oil index, seed protein %, embryo protein % and physical seed properties, embryo index, seed index, 100-seed volume and embryo %. The heritability estimates were high for seed coat protein %, moisture content %, seed oil %, seed free fatty acid, embryo add value and embryo index and 100- seed volume. Moderate h2 were recorded for seed index, seed density and embryo oil index, while it was low for the other seven traits. Very close estimates of genotypic and phenotypic coefficients of variation are used for assessment of variability for boll weight, embryo free fatty acid and embryo acid value. The studied genotypes were divided into two clusters with similarity index (36.99%) and distance level (8.98). The first cluster group hybrid (G.68xG.45) x ((G.84 xG.45) x G.45).The two-cluster group divided into two subgroups, the first of them represented the genotype (G.84 x F. 108) x ((G. 84 xG.45) x G.45) and the commercial variety G. 70, While the second included the other. genotypes with a similarity index of (71.52%) and distance level of (4.06).