Target foil stacks of niobium were bombarded with beams of alpha particles at incident energies ranging from 0 to 90 MeV. Cumulative cross sections for the production of95(m+g)Nb,92mNb,91mNb and90(m+g)Nb were determined by semiconductor gamma-spectrometry of the residual activity of stacked foils. On the basis of the cumulative cross sections, the thick target yields and saturation production rates of niobium isotopes have been evaluated.