The paper investigates a M/M(b,b)/1 queuing model with bulk service. The server serves the customers in batches of fixed size b, and the service time is assumed to be exponentially distribution. Customers arrive to the system as a Poisson process and may renege after waiting in the queue for an exponentially distributed time. The reneging of a customer depends on the state of the system. The model is analyzed to find the different measures of effectiveness of the model. The approach adopted is based on embedded Markov chains. © 2017, Thai Statistical Association. All rights reserved.