Gibberellins are bioregulators associated with yam tuber dormancy. When yam tubers were dipped in GA3 solution at concentration from 100-1000 ppm bud breaking never ocurred. Furthermore, bud breaking was delayed by three folds with GA3 at 1 ppm compared with the control. Similar effects were found with Promalin at concentration from 1-1000 ppm. Daminozide and Paclobutrazole also extended dormancy but in a less degree. None of the treatments inhibited the dormancy period compared with the control. Experiments were design to characterize giberellins in yam tubers. Methanol and ethyl acetate extracts were prepared from tuber tissue. Extracts were purified by adsortion chromatography using a polyvinylpolypirrolidone column followed by charcoal-celite column. Further purification was made using C-18 reversed phase HPLC. Fractions with biological activity were detected by the lettuce hypocotyl bioassay.