AC self-field losses and DC dynamic resistivity in HTSC conductor elements have been measured. The data are discussed with reference to the relevant theory. For two very different sample types, the J/sub c/ calculated on the basis of the AC self-field loss is about an order of magnitude lower than the J/sub c/ based on the 1- mu V/cm DC voltage drop criterion often used for HTSC materials. This is attributed to the onset of resistive behavior at currents much lower than the reported J/sub c/ based on the 1- mu V/cm criterion. The J/sub c/ determined from measurements of the dynamic resistivity of a melt-textured YBCO fiber is within 15% of that determined by magnetic measurements. >