OBJECTIVE: To compare the preoperative effects of multidimensional land-based and pool-based exercise programs for people awaiting joint replacement surgery of the hip or knee. DESIGN: Randomized, single-blind, before-after trial. SETTING: Physiotherapy gymnasium and hydrotherapy pool. PARTICIPANTS: Patients awaiting elective hip or knee joint replacement surgery. INTERVENTIONS: Land-based (n=40) or pool-based exercise program (n=42). Each 6-week program included an education session, twice-weekly exercise classes, and an occupational therapy home assessment. MAIN OUTCOME MEASURES: Participants were assessed immediately before and after the 6-week intervention, then 8 weeks later. Primary outcomes were pain and self-reported function (Western Ontario and McMaster Universities Osteoarthritis Index) and patient global assessment. Secondary outcomes were performance-based measures (timed walk and chair stand) and psychosocial status (Medical Outcomes Study 36-Item Short-Form Health Survey mental component score). Pain was also measured before and after each exercise class on a 7-point verbal rating scale. RESULTS: Although both interventions were effective in reducing pain and improving function, there were no postintervention differences between the groups for the primary and secondary outcomes. However, the pool-based group had less pain immediately after the exercise classes. CONCLUSIONS: While our multidimensional exercise-based interventions appeared to be effective in reducing disability in those awaiting joint replacement surgery of the hip or knee, there were no large differences in the postintervention effects of the interventions. However, pool-based exercise appeared to have a more favorable effect on pain immediately after the exercise classes.