A six-pool, full-scale section of the 1-on-10-slope Ice Harbor fishway design was built and tested in the Fisheries-Engineering Research Laboratory at Bonneville Dam before constructing the prototype. Performance of chinook salmon (Oncorhynchus tshawytscha), steelhead trout (Salmo gairdneri), and sockeye salmon (O. nerka) was examined in a series of tests. Results were compared with data from previous tests with a 1-on-16-slope fishway. These comparisons indicate that the new 1-on-10-slope fishway will pass fish as efficiently as the conventional 1-on-16-slope fishway. Several modifications of the original design were examined and minor changes in it was recommended. Responses of fish to various flow conditions in the test fishway also were noted and velocity profiles obtained in several typical pools.