An attempt is made to meet the need for a single standardized growth equation to cover the entire period from conception to adulthood in a wide range of mammalian species. It is suggested that an ideal equation is one which adequately describes the overall shape of a growth curve and, in addition, can be extended or modified to give greater flexibility and higher precision as necessary. The structure of such an equation is discussed and results in the derivation of a logistic relationship between adjustable ‘flexibility’ functions of size and time.

Data from eight species are examined and in both its basic and extended forms the equation is found to give acceptable fits to individual species and to provide a useful mean standardized growth curve for mammals.