We consider a machine interference problem with several types of machines attended by a single repairman. Assuming exponentially distributed time to failures, generally distributed repair times arid head of the line non-preemptive priority repair discipline, an imbedded Markov chain model is formulated. Using this Markov chain model and a discrete state level crossing analysis the steady state probability distribution of the number of machines in failed state at an arbitrary time epoch is derived. An algorithm is developed to compute these probabilities and some numerical results illustrating some basic features of this machine interference problem is also presented