This paper studies the individual loss probabilities for two call types having different mean holding times (MHTs) when they share a circuit group in an integrated services network. Our model takes into account both Poisson calls and overflow calls. We obtained two important results regarding the effect of different MHTs: (1) the loss probability becomes larger for calls of shorter MHT, and smaller for longer MHT, and (2) the influence of MHT is especially pronounced in the case of overflow calls.