The mixing process of opposing jets by coaxial impingement in the mixing chamber of a reaction injection molding has not been clarified. This paper presents the results obtained from numerical experiments for the coaxial impingement of opposing laminar jets. The numerical solution of Navier-Stokes equations is obtained by a finite-difference approximation which is extended from the exisiting solution for a laminar jet. The effects of the jet Reynolds number, the velocity profile at the nozzle exit and the distance from the nozzle to the impingement surface on the flow after the impingement are shown, and their effects on the flow mixing of the two jets are discussed.