An experimental fishway was used to examine adult Pacific lamprey, Lampetra tridentata (Gairdner), behaviour in a series of attraction and passage-performance tests. Among all experiments, lamprey oriented to the fishway floor and walls and were attracted to both ambient and concentrated flow. When confronted with highvelocity areas (vertical-slot and submerged-orifice weirs), many lamprey failed to pass upstream. However, lamprey were able to find and take advantage of low-velocity refuges when they were provided. Lamprey climbed shallow-and steep-angled ramps when attraction cues were sufficient and other passage routes were restricted. The combined results demonstrated the passage challenges that fishways designed and operated for salmonids present to non-salmonid species. They also highlight the importance of evaluating trade-offs between fishway attraction and passage efficiency. The experiments were integrated with tagging studies and development of lamprey-specific passage structures, a research combination that provided an effective template for fishway performance evaluations.K E Y W O R D S : burst swimming, Columbia River, fishway performance, migration barrier, rheotaxis, velocity refuge.