The extensive fragmentation of riverine habitat in the United States Great Plains region can be mitigated through the use of fish passage structures designed with appropriate fish performance data. Many of the fish in this region can be characterized by their relatively small body size (adult TL < 30 cm) and their unwillingness to attempt to jump over instream obstacles. We measured the effects of slope (2, 4, 6, 8, and 10%) on the passage success of three representative species of fish from this region in a variable geometry 6.1-m long rock ramp fishway using multiple PIT tag antennas to determine how far up the fishway each fish travelled. The species selected represent a spectrum of relative swimming ability, from the strongly-swimming Flathead Chub (Cyprinidae: Platygobio gracilis), to the intermediate-swimming Stonecat (Ictaluridae: Noturus flavus), and the poor-swimming Arkansas Darter (Percidae: Etheostoma cragini). Passage success varied by species, with Flathead Chub negotiating steeper and longer fishways than Stonecats, who were in turn better performers than Arkansas Darters. As expected, reducing fishway length and decreasing fishway slope increased the probability of successful passage for all species. A second set of experiments quantifying the passage of the same three species in the test fishway when a 180-degree bend was included as part of a 4% slope fishway was also conducted. The addition of the bend did not materially affect overall passage success for the species tested. Our results allowed us to propose fishway design criteria based upon fishway slope and length combinations that improve the passage probability of these representative small-bodied Great Plains fishes.