The aim of this investigation was to estimate combining abilities for yield, yield component traits and fiber properties in cotton. The genetic materials used in the present study included 45 F₂ double crosses. In 2010 growing season, these genotypes were evaluated in a field trial experiment at Sakha Agricultural Research Station, Kafr El-Sheikh Governorate for the following traits: seed cotton yield/plant (S.C.Y./P.), lint yield/plant (L.Y./P.), boll weight (BW), lint percentage (L.%), fiber fineness (F.F), fiber strength (F.S) and upper half mean (UHM). The results showed that the mean squares of genotypes were highly significant for all studied traits except (L. %)., the partitioning of the double crosses mean squares to its components showed that the mean square due to 1-line general, 2-line specific, 2-line arrangement, 3-line arrangement and 4-line arrangement were either significant or highly significant for most studied traits.These results  suggesting the presence of the additive and non-additive genetic variances in the inheritance of these traits . The parents Giza 86 (P₁) and TNB1 (P₂) were  the best general combiner for most studied yield component traits and  fiber properties . The parental variety C.B 58 ( P₄)  showed positive and desirable values of general combining ability among  parents for  fiber fineness (F.F.) . The parent Giza 85 (P₅) was good combiner for lint percentage, while, the parent Suvin (P₃) was the best combiner for most yield component traits. Concerning the two-line interaction effect, (S²₁₂), (S²₁₃), (S²₁₅), (S²₂₃) and (S²₄₆) showed positive (desirable) effects for most yield components. Moreover, the best combinations for (F.F) were (S²₁₂), (S²₃₅) and (S²₄₆). Also, the best combinations for (F.S) and (UHM) were (S²₁₆), (S²₂₃) and (S²₄₆), respectively. The three-line interaction effect cleared that the combinations (S³₁₂₃), (S³₁₂₅), (S³₁₃₅) and (S³₂₃₅), (S³₂₄₆), (S³₄₅₆) showed great positive (desirable) effects for seed cotton yield/plant (S.C.Y./P.) and lint yield/plant (L.Y./P.). In the same time, (S³₁₃₅), (S³₁₄₅), (S³₁₄₆), (S³₁₅₆), (S³₂₃₆) and (S³₂₄₆) were the best combinations for (F.S), while (S³₁₂₃), (S³₁₅₆), (S³₂₃₄), (S³₂₄₆) and (S³₃₄₆) for (UHM) as well as [(S³₁₂₃), (S³₁₂₄), (S³₁₄₆) and (S³₂₃₅)] for (F.F) property.  Furthermore, the four-line interaction effect revealed that the best double cross combinations for (S.C.Y. /P.), (L.Y. /P.) was (S⁴₁₂₃₅). Moreover, (S⁴₂₄₅₆), (S⁴₁₃₄₅), (S⁴₁₂₄₆), (S⁴₁₂₅₆) and (S⁴₁₄₅₆) were the best double combinations for (B.W), (L. %), (F.F), (UHM) and (F.S), respectively. The specific combining ability effects t²(ij)(..) showed that the combinations t²(16)(..), t²(₂₄)(..), t²(₅₆)(..), t²(₃₆)(..), and t²(₁₅)(..) were the best combinations for (S.C.Y. /P.), (L.Y. /P.), (L. %), (B.W), (F.F), (UHM) and (F.S) traits, respectively. In conclusion, from the preivous results it could be concluded that the combinations [(P₁ x P₂) x (P₃ x P₅)] and [(P₁ x P₂) x (P₄ x P₆)] appeared to be the best promising double crosses for breeding of yield traits .   In general, [(P₁ x P₅) x (P₂ x P₄)], [(P₁ x P₅) x (P₃ x P₆)] and [(P₂ x P₄) x (P₃ x P₆)] would be good combinations for most studied yield and fiber traits. Meanwhile, [(P₁ x P₄) x (P₂ x P₃)], [(P₁ x P₄) x (P₅ x P₆)] and [(P₂ x P₃) x (P₅x P₆)] would be the best for most studied yield traits and fiber strength (F.S.) property. In addition, the combinations [(P₁ x P₆) x (P₂ x P₃)], [(P₁ x P₆) x (P₄ x P₅)], [(P₂ x P₃) x (P₄ x P₅)]and [(P₂ x P₅) x (P₄ x P₆)]appeared to be the best promising for upper half mean (UHM) property.The results revealed that the magnitudes of dominance genetic variance (σ²D) were positive and larger than those of additive genetic variance (σ²A), for most studied traits. Concerning epistatic variances, additive by dominance genetic variance (s²AD), additive by additive genetic variance (s²AA) and additive by additive by additive genetic variance (s²AAA) played a major role in the inhertance of yield components and fiber properties traits. This finding may explain the superiority of most studied double crosses than their parents in most of yield components traits. Therefore, it could be recommended that production of double crosses to involved in the selection breeding programs is the desirable way for improvement these traits.