Isokinetic and static maximum plantar flexion torques were measured in 135 adults with sedentary professions. Close associations between isokinetic and static peak torques were found. Between the ages 20--49 years strength did not differ. Thereafter strength declined as a function of age. Maximum strength was 35% lower in females than in males. The right plantar flexion strength was slightly lower than the left. Maximum plantar flexion strength was about 15% lower with flexed than with extended knees. A negative exponential model characterized the decline of strength as a function of increased isokinetic velocity of angular motion. Seventy per cent or more of the variations in maximum static and isokinetic strength could be explained by anthropometric variables and by age, and by the extent of physical activity in subjects younger than 50 years. Formulas for estimation of expected static and isokinetic strengths are given.