The dose of most cancer chemotherapeutic drugs administered to dogs is calculated on the basis of estimated body surface area (BSA); however results of some chemotherapy trials have revealed that this dosing method increases toxicosis in small dogs. The current formula used to estimate BSA in dogs may be inaccurate or the assumption that BSA correlates with chemotherapeutic drug exposure may be unfounded. Results presented in this review suggest that canine BSA estimates may be inaccurate because the values for the constant (K) and exponent (a) in the formulae (BSA = K.Wa) are incorrect or because a linear parameter such as body length is lacking from the formulae. Results that suggest the relationship between BSA and the physiologic/pharmacologic factors that influence drug exposure may not be closely correlated are also presented. Studies are warranted to determine whether there are dosing methods that normalize chemotherapeutic drug toxicity in dogs.