MILLER, W. C., J. P. WALLACE, and K. E. EGGERT. Predicting max HR and the HR-V̇2 relationship for exercise prescription in obesity. Med. Sci. Sports Exerc., Vol. 25, No. 9, pp. 1077–1081, 1993. This research derived regression equations for predicting maximal heart rate (MHR) and examined the relationship between relative oxygen consumption (V̇2) and heart rate (HR) in obese (N = 86, body fat > 30%, hydrostatic weighing) compared with normal-weight (N = 51, body fat ≤ 30%) adults. Simultaneous measurements of HR and V̇2 were recorded at rest and every minute during a maximal graded exercise test. When MHR was regressed on age, two distinct equations for the obese and normalweights were generated. The relationship between %MHR and %max V̇2 was similar between groups (r = 0.83, obese; r = 0.87 normalweights). Likewise, when %max V̇2 was regressed on %max heart rate range similar equations were derived for the obese (r = 0.81) and normalweights (r = 0.84). Correlation between Karvonen's predicted HR at a submaximal V̇2 and the true HR at that V̇2 was 0.88, regardless of adiposity. These data indicate that when predicting MHR in normal-weights the equation 220-Age can be used, but for obese individuals the equation 200 - 0.5 × Age is more accurate; each having 12 as a standard error of estimate. Once MHR is determined, either the straight percentage technique or Karvonen's method would be appropriate for prescribing exercise intensity for both populations.