Using cDNA Representational Difference Analysis (RDA) techniques, we isolated a cDNA that was expressed specifically in cotton fibers but not in the ovules of a fuzzless-lintless mutant (fl). We designated it as Gh-BTubL for it shares high sequence identity with known plant and yeast beta-tubulins. RT-PCR and robotic cDNA dot blot analyses indicated that the expression of Gh-BTubL was correlated with the elongation pattern of cotton fibers. In situ hybridization results verified that there was no Gh-BTubL mRNA in fl ovules while it was easily detected in the elongating wild type cotton fiber cells. Overexpression of Gh-BTubL in fission yeast induced longitudinal growth of the host cells by 1.74-fold, with no apparent effect on other aspects of the host cells. We suggest that Gh-BTubL plays an important role in cotton fiber elongation and we believe that elucidation of the control mechanisms for expression of tubulin-like proteins may help improve fiber quality and productivity.