The initial stage crystallization of the A(x)(III)B(1-X)(III)C(V) quasibinary alloys from the supercooled dilute liquid solutions is considered. Nonequilibrium crystallization is presented by the minimum condition of the Helmholtz free energy. A model of the regular solutions is used for the description of the liquid and solid phases. The compositional dependencies of the GaxAl1-xAs and InxGa1-xP alloys on temperature and supercooling of the liquid solutions are demonstrated. The affinities of the formation reactions of binary compounds constituting the A(x)(III)B(1-x)(III)C(V) alloys are equal one another. Ratios between the affinities and temperature in the energy units are substantially smaller than unity for all considered growth processes.