Detecting Random Amplified Polymorphic DNA (RAPD) markers to identify fiber strength genes in cotton was approached. Presence or absence of four PCR-amplified DNA fragments was related to the bundle fiber strength of cotton fibers. Of 120 random primers, 111 had matching sequences on genomic DNA of the three pairs of sib-lines which were selected for consistent performance in difference of fiber strength for three years. DNA polymorphisms between the two corresponding sib-lines were detected with 22 of the 111 random primers. Of the 22 primers, 19 primers at least resulted in DNA polymorphisms between Gossypium hirsutum acc. TM-1 and G. barbadense acc. 3-79. Presence or absence of six PCR-amplified DNA fragments with three primers was significantly related to the bundle fiber strength of 40 individuals of (TM-lx3-79)F₂ population. Three of the DNA fragments were paired with one of the parents. The other was paired with both parents. These DNA fragments are being isolated and evaluated as standard RFLP markers.