© Serdi and Springer-Verlag International SAS, part of Springer Nature. Objective: To determine normative values for weight-bearing, countermovement leg extension (“jump”) tests in the oldest men and characteristics of those not completing vs. completing tests. Design: 2014-16 cross-sectional exam. Setting: Six U.S. sites from the Osteoporotic Fractures in Men (MrOS) Study. Participants: Community-dwelling men (N=1,841) aged 84.5±4.2 (range: 77-101) years. Interventions: N/A. Measurements: Jump tests on a force plate measured lower-extremity muscle peak power/kg, velocity and force/kg at peak power, with normative values for 5-year age groups and by limitations in moderate-intensity activities of daily living (ADLs) and climbing several flights of stairs. Results: Jump completion was 68.9% (N=1,268/1,841) and 98% (1,242/1,268) had >1 analyzable trial/participant. Exclusions primarily were due to poor mobility and/or balance: 24.8% (456/1,841) prior to and 6.4% (N=117/1,841) after attempting testing. Peak power was 20.8±5.3 W/kg, with 1.2±0.3 m/s for velocity, and 16.7±1.9 N/kg for force at peak power. Each 5-year age group >80 years had subsequently 10% lower power/kg, with 30% lower power/kg at >90 vs. <80 years (all p<0.05). Velocity and force/kg at peak power were 24% and 9% lower respectively, at >90 vs. <80 years (all p<0.05). Limitations in both moderate ADLs and climbing several flights of stairs were associated with 16% lower ageadjusted power/kg, equivalent to 5-10 years of aging, with 11% and 6% lower age-adjusted velocity and force/ kg respectively, vs. those without limitation (all p<0.05). Men not completing vs. completing jumps had older age, higher BMI, lower physical activity, more comorbidities, worse cognition, more IADLs/ADLs and more falls in the past year (all p<0.05). Post-jump pain occurred in 4.6% (58/1,268), with 2 participants stopping testing due to pain. Only 24/1,242 (2%) had all trials/participant without flight (i.e., inability to lift feet), with 323/1,242 having ≥1 trial/participant without flight (total of 28%). No serious adverse safety events (e.g., injury) occurred. Conclusions: A multicenter cohort of oldest men with a range of function had higher declines in jump power/kg and velocity vs. force/kg across each 5-year age group >80 years. Future research should examine ageand functional-related declines in jump measures related to physical performance decline, falls, fractures, and disability.