For YBCO epitaxial thin films the basal plane transport critical current densityJc, flowing perpendicular to an applied magnetic fieldH, depends sensitively on the orientation of the crystal with respect toH. In particular,Jcis sharply peaked and greatly enhanced whenHis precisely parallel to the copper‐oxygen planes. Experiments on a series of epitaxial monolithic and superconductor‐insulator multilayer thin films provide clear evidence that the enhancement is a bulk, rather than surface or thin sample, phenomenon. Measurements of the orientation dependence are presented and compared with a model of ‘‘intrinsic flux pinning’’ by the layered crystal structure.