This paper presents the results of a simulation study of a just–in–time (JIT) production control system and its performance under different operational conditions. In particular, the effects of two different kanban withdrawal policies on such performance measures as throughput rate, station utilizations and total work in process levels are investigated. Also, simulation experiments are carried out to determine the effects of processing time variability, number of different types of kanbans allowed at each station and production line length on the mentioned performance measures of JIT production control method. The simulation experiments were carried out for production lines in which processing times of stations were assumed to follow gamma and Erlang distributions.