This investigation was carried out at Sakha Agric. Res. Stat. KafrelSheikh, Agric. Res. Centre, Egypt, during 2014 and 2015 growing seasons. A study was undertaken on some genotypes of Egyptian cotton (Gossypium barbadense L.) to estimate the mean performance, heterosis over better parent (heterobeltiosis), combining ability and type of gene action for some earliness, yield and its components traits in some Egyptian cotton genotypes by using line x tester mating design between seven cotton genotypes i.e., Giza 45, Giza 67, Giza 68, Giza 85 Giza 86, Dandra and Giza 92 which used as lines, and two foreign varieties; Pima S6, Karsheneski-2 as well as promising cross Giza 89 x Pima S6 were used as testers. The analysis of variance indicated that the mean squares of genotypes for all studied characters were significant and highly significant, indicating the present of considerable amount of genetic variability among genotypes, parents and hybrids. Mean squares of general combining ability general combining ability (GCA) for lines found to be signification for most investigated characters. On the same time general combining ability variance for testers (female parents) were also significant for earliness index , boll weight, seed and lint yield / plant , seed index and lint index. These revealing important of additive and additive x additive type of gene effect on such characters. While, the mean squares of specific combining ability (SCA) were also significant for all yield and it's attributed characters, except for first fruiting node, revealing that non-additive (dominance or epistasis) effects in the inheritance of these traits was detected. The data illustrated that the variance due to general combining ability was lower than variance of specific combining ability and the ratio of s2 GCA / s2 SCA was less than unity for all studied characters, indicating preponderance of non–additive gene action (dominance or epistasis), which is an important in exploitation of hetorsis through hybrid breeding. The cross combination Kar2 x Giza 85 followed by Kar2 x Giza 67 surpassed all cross combinations for earliness index. The cross combinations Pima x 67, Pima x 86 and Pima x 68 exhibited mean values and exceeded other combinations for yield and its components traits. The cross combination Kar2 x G.67 recorded the best values of heterobeltiosis for all earliness traits followed by Kar2 x G.86. The cross combination Pima x G.68 recorded significant desirable values over better parents heterosis for seed cotton yield/ plant, lint yield and lint percentage. Karshenesky2 was the best combiner for earliness index and seed volume. Giza 67 was the best general combiner for earliness index. The parent Giza 68 recorded significant positive general combining ability value for seed cotton yield/ plant. However, the parent Giza 85 followed by Dandra gave the best general combining values for lint yield / plant and lint percentage. The cross combination Kar2 x Giza 92 was the best combination for most earliness characters. However, the cross combination Pima x 67 followed by Pima x Dandra observed highest positive significant SCA effects for most yield characters.