Two global ocean data assimilation systems are evaluated and compared. One is from the Global Modeling and Assimilation Office (GMAO, formerly the NASA Seasonal-to-Interannual Prediction Project, NSIPP) at the NASA Goddard Space Flight Center, the other from the Geophysical Fluid Dynamics Laboratory (GFDL) at NOAA. As part of the effort by the Consortium for Ocean Data Assimilation for Seasonal-to-Interannual Prediction (ODASI), an activity of NOAA's CDEP, assimilations are run for ten years from January 1993 to December 2002. The ODASI consortium is focused towards improving ocean data assimilation methods and their implementation in support of forecasts with coupled general circulation models. The same forcing dataset and observation data streams are used to facilitate the intercomparison of the results. By comparing different assimilation schemes and their implementations in different models, we can improve our understanding of ocean assimilation processes so as to accelerate our progress in improving coupled model forecast skill using best analyses of ocean state as the initial condition.