Abstract : Light-cone quantization proceeds through Dirac's Front Form and needs a procedure for the handling of dynamical constranits. It is treated of The phi4 (1+1) theory is examined with the help of a continuum formulation of the fields and zero modes Haag expansion (CLCQ). This allowed an original solution of the equations of motion and the constraints, as well as a consistant infrared and ultraviolet divergences renormalization. Phase transition analysis shows second order non perturbative critical coupling constant similar to conventionnal methods fourth order results Comparative study of discrete and continuum Pauli-jordan commutator formulations demonstrates that violation of causality is nothing else a finite volume effect linked with zero modes substraction in discretes sums. The study of phi4 (3+1) O(N) theory is begun with order 3 fields and zero modes 1/sqrt(N) expansion which enables to get, up to the 1/N^3, the same conventionnal correlation functions obtained by path integration.