This paper deais with the steady-state behaviour of a queueing proeess in which units demanding one phase or two phase service arrivo with a Porssoa stream and form two queues Q₁ and Q₂ in front, of two service channels S₁ and S₂respectively.Furthermore units demanding two phase service join a single queue Q₃ for the completion of their service in front of another server S₃ of the system after getting the first.phase service from S₁ or S₂.If we assume ordered service as our queue discipline and exponential service times for each channel, then we drive for the system steady-state mean queue lengths and some particular cases thereof.