The possibility of improving the cold formability of wrought magnesium alloys is considered in light of their good hot forming characteristics. Magnesium alloy AZ31B sheet is selected as a model system. Parameters affecting formability, such as strain hardening rate, strain rate sensitivity, and the degree of anisotropy are examined systematically by conducting tensile tests over a range of temperatures (room temperature to 250degreesC) and strain rates (1 x 10(-5) to 0.1 s(-1)). The plastic anisotropy and deformation texture evolution are examined in samples aligned with the sheet rolling and transverse directions. Polycrystal plasticity simulations using a viscoplastic self-consistent (VPSC) formulation are used to model the observed anisotropy and texture evolution. The adjustable parameters in the model are the relative critical resolved shear stresses of the dislocation mechanisms known to operate within magnesium. The experimental results suggest that an increased strain rate sensitivity is the most important macroscopic change responsible for inducing the formability observed at high temperatures. The polycrystal simulations indicate that an increased activity of non-basal, dislocations provides a self-consistent explanation for the observed changes in the rate sensitivity, anisotropy, and texture evolution with increasing temperature.