In this paper, we use internal pressure to predict metal-nonmetal transitions in alkali metals. Isotherms of the internal pressure of cesium fluid versus molar volume show a maximum point around 1.3 g.cm(-3) in agreement with X-ray diffraction and small-angle X-ray scattering. It is shown that at molar volumes higher than the maximum point the attractive force has a strong influence on the determination of internal pressure that similar studies have been made for negative compressibility. An accurate empirical potential was found for dense alkali fluids and used to test the applicability of the theory. These theoretical predictions are in good agreement with experimental results. Problems have led us to try to establish a function for the accurate calculation of the internal pressure and the prediction of metal-nonmetal transition alkali metals based on the internal pressure.