Merit, defined as goodness of performance on jobs at a given level in an organization, often is used as a basis for the selection of persons for advancement so as to fill vacant positions at higher levels. By means of a simple mathematical model it was shown that structural properties of organizations bear upon the efficacy of merit as a basis for filling vacant positions. In general, advancement on the basis of merit is found to be most effective in organizations which have large spans of control, are homogeneous, and are flat in shape. © 1969.