Verification is an essential part of the forecast process that provides guidance on the statistical behavior of the system and a framework by which a forecast can be assessed for its "goodness." Much of the framework applicable to ocean forecasting has been developed within the atmospheric community. A review of the available material is given with some commentary on its relevance in the context of ocean forecasting. A statistical theory is presented for errors in an ocean forecast system (both deterministic and ensemble) and for a number of verification metrics. Theoretical results are demonstrated with empirical models and results from an operational ocean forecast system. Some new results are presented comparing the mean absolute error and root mean square error and the inference hypothesis testing of ensemble forecast systems. The progress in ocean verification is discussed, as are advances in technology to analyze international verification databases.