made? H F RADARS ARE A UNIQUE and powerful tool for measuring surface currents. They provide an unpa ra l l e l ed window into the spat ial var ia t ions of near-surface currents. But oceanographers who are more accus tomed to measur ing currents with instruments that actually get wet may reasonably ask how accurate can such remote measurements be made? And whi le this is an easy and obv ious question to ask, it is an interestingly difficult question to answer. We have been s tudying the accuracy of the OSCR HF radar system through analysis of data from the Office of Naval Research (ONR)-sponsored High-Reso lu t ion Remote -Sens ing Exper i ment that was conducted off Cape Hatteras, North Carolina during the summer of 1993. This experiment provided a unique opportunity to examine the complex quest ions of HF radar accuracy. Along with several weeks of HF radar data, we had access to mult iple in situ measurements of current from both moored and ship-based devices. In a series of ana lyses , we have a t t empted to va l ida te the HF current measurements through comparison with the in situ data, The key has been to examine the temporal and spatial var ia t ions within these data in order to dist inguish the sources of the underlying differences between the systems we compare.