Corn yields and leaf samples vere obtained from experimental plots receiving various rates and combinations of N, P and K. Yields were regressed on leaf N, P, K, Ca and Mg as independent variables expressed in milliequivalents per 100 grams and percentages in three regression models. The fit of two models was shown to be equivalent regardless of method of expressing the independent variables. For the other model the choice of milliequivalents per 100 grams or percentages determines a unique function.