In several recent article, Heusner used dimensional reasoning to derive important biological conclusions regarding the scaling of metabolism with body mass [Respir. Physiol. 48: 13-25, 1982; J. Appl. Physiol. 54: 867-873, 1983; Am. J. Physiol. 246 (Regulatory Integrative Comp. Physiol. 15): R839-R845, 1984]. We demonstrate errors in the derivation and show that dimensional analysis, correctly applied, not only fails to determine the mass scaling exponent but also fails to constrain the relationship to a power law at all.