The objective of this study was to determine the effects of osmo and hydro-priming on phenology, yield components and biomass yield of soybean (Glycine max) cv. William-82. After a laboratory experiment to determine the optimum combination of priming duration and polyethylene glycol 8000 (PEG 8000) concentration, field experiment was conducted in 2003 and 2004 with three priming durations (6, 12 and 18 h) and five different concentrations of PEG 8000 solution (0, -0.2, -0.5, -1.1, -1.8 , -3.0 and -4.2 MPa), together with a dry seed (non primed) control. Primed and non-primed seeds were sown in the field. During both years, plants from primed seed flowered and matured faster than plants from non-primed seed. Primed seed gave taller plants. Averaged over all treatments, priming for 6 h or with -1.1 MPa, were the most beneficial treatments. It is concluded that priming with PEG was much effective but priming with water alone was also better than control.