One hundred twenty-eight healthy volunteers (81 women, 47 men) older than 55 yr off age were studied with an incremental progressive cycle ergometer test to a symptom-limited, maximal tolerable work load. Mean (± SD) age was 66 ± 6 yr in women and 66 ± 5 years in men. Subjects with a history off ischemic heart disease, diabetes, pulmonary disease, or neuromuscular disease were excluded. Smokers were included, but all subjects had normal FEV₁ and FVC. The objective of the study was to compare measured values of o₂max and Ẇmax in this older population with previously published predicted values based on subjects of all ages. We found that Ẇmax observed exceeded Ẇmax predicted by 9.5 ± 22% (mean ± SD) and that o₂max observed exceeded o₂max predicted by 17.5 ± 22%. Because of this systematic underestimate of o₂max and Ẇmax by the previous prediction equations, we constructed new prediction equations for use in subjects older than 55 yr of age using height, weight, age,and sex as variables. We conclude that these new prediction equations more accurately predict Wmax and o₂max in subjects older than 55 yr of age because they are based solely on subjects in this age group.