The field emission current density j from the ternary alloy AlxGa1-xN is fully calculated as a function of a stoichiometric composition x. The carrier concentration. n is numerically obtained as a function of x from the measured values of n. Most of the other material parameters of AlxGa1-xN are obtained,as a function of x by averaging those of GaN and AlN. Then we use an exact scheme to calculate j as a function of x for x less than or equal to 0.7. The calculated plots of j versus x are different in shape according to the value of electron affinity, x, of AlxGa1-xN. For low x, j has a peak in the transition region, from semiconductor to insulator while for high X, j does not. Such a peak becomes more apparent and moves toward a smaller x as x decreases and the field F increases. (C) 2003 American Vacuum Society.