This paper studies the effect of interleaving operation on the bifurcation behaviour in a system of parallel-connected dc/dc buck converters. Simulations and analysis are presented for both the cases of interleaving and synchronous operations. The effects of variation of some chosen parameters on the bifurcation behaviour of the system are captured. In particular, it is found that variation of the voltage feedback gains leads to period-doubling bifurcation. Interleaving operation will discourage the occurrence of this bifurcation by widening the stable region. It is also observed that variation of output capacitance, load or switching period leads to Neimark-Sacker bifurcation. Interleaving operation will make this bifurcation more likely to occur by narrowing the stable region. In order to show the effect of interleaving operation, bifurcation boundaries of stable period-1 operation in the two cases are located and compared.