Alston and Chalfant&s least squares test for functional form is biased. A valid test is derived for both univariate and multivariate regression models. An estimation method to account for endogenous left- and right-hand-side current-period budget shares in the Rotterdam and LA-AIDS models is presented. Alston and Chalfant&s strenuous rejection of the LA-AIDS model in favor of the Rotterdam model is not supported by their data. Copyright 1998, Oxford University Press.