Microstructure and critical current densities of laser ablated YBa2Cu3O7-delta thin films doped with 2-20 wt. % Ag have been studied. A critical current density as high as 1.4 X 10(7) A cm-2 at 77 K has been realized on [100] SrTiO3 substrates with YBaCuO films doped with 5 wt. % Ag which has been found to be the optimum. Evidence indicates that the improved microstructure and epitaxy which is a consequence of grain enlargement and alignment caused by Ag is responsible for the high values of critical currents observed.