Here, we present an analysis for an M/M/C feedback queueing system with reneging. The customers arrive at the queueing system according to Poisson process. Inter-arrival time and service time follow the exponential distribution. Customers may leave the system after joining the queue without getting service due to impatience. It is assumed that customers renege according to exponential distribution/ fixed probability. Steady-state queue-length probabilities & Laplace transformation of the probability generating function of busy period distribution are obtained. Some important results are derived by considering particular cases
of this model.