In this paper, the strong stabilization problem of multivariable linear time-invariant systems is considered. The problem is categorized into minimum and non-minimum phase systems. When the given system is minimum phase, the solution requires a stable inverse of a particular stable transfer function matrix; while for a non-minimum phase system, the solution requires an inner-outer factorization, whose outer part is unimodular in RHinfinity and an interpolation in RHinfinity. The formulation of the two cases will be modified so that the conditions for the existence of stable inverse or unimodularity of the outer part are satisfied. When the system is strictly proper it is shown that the problem is more technically involved.