Fiber length is one of the most important properties of cotton fi bers, with longer fi bers allowing for faster processing speeds and a wider array of end products. Four elite, near-longstaple upland cotton (Gossypium hirsutum L.) genotypes with diverse programmatic origins, TAM 94L-25, Fibermax 832, TTU 202, and Acala 1517-99, and one short-staple genotype, Tamcot CAMD-E, were crossed and evaluated in a diallel without reciprocals for six fi ber-length measurements at College Station, TX, in 2001 and 2002. Genotypic variation (P ≤ 0.05) and signifi cant general combining ability (GCA) were identifi ed for upper-half mean length (UHML), fi ber length by weight (FLw), fi ber length by number (FLn), and upper-quartile length by weight (UQLw). Signifi cant variation for specifi c combining ability (SCA) was identifi ed for FLw, FLn, and shortfi ber content by weight (SFCw). Fibermax 832 exhibited the longest fi bers for all length measurements, but TAM 94L-25 had the highest GCA effects for UHML, FLw, FLn, and UQLw and thus would be the best parent to use in parental combinations to improve fi ber length. The highest desirable SCA effects resulted from the Fibermax 832 × Acala 1517-99 combination. Combining- ability data among these genotypes, which represented diverse U.S. germplasm pools, suggest that most U.S. cotton breeding programs could improve fi ber length by using TAM 94L-25 in combination with their breeding lines.