We have measured the critical current in Nb strips of 1 Μm thickness and different widths w prepared by electron-gun vacuum deposition. The substrate temperature during the deposition was varied between room temperature and 800 ° C. The width of the Nb strips ranged between 20 and 300 Μm. Whereas up to 600 ° C the different substrate temperatures yielded about the same critical current density J c (critical current divided by sample cross section), the specimens prepared with 800 ° C substrate temperature showed a reduction of J c by a factor of 4–6. In zero applied magnetic field the samples prepared with 400 ° C substrate temperature or lower showed a decrease of J c roughly proportional to w -1/2. Such behavior can be understood from a homogeneous and field-independent pinning-force density. Our critical current data obtained in an applied perpendicular field, for the high-field regime, were compared with Kramer's theory of flux pinning, which assumes plastic shearing of the flux-line lattice around individual pinning sites during flux flow.