A criterion for identifying the squeezing potential of tunnel is proposed. Tunneling conditions, classified as slightly or non-squeezing, moderately squeezing and highly squeezing, were identified by relating the strength-stress (cr,m/Po) ratio to the development of plastic zone extent and the amount of tunnel closure. Actual case histories of tunneling in Taiwan show that this criterion predicts the tunnel performance quite well. This enables the identification of tunneling conditionsexpected which require special considerations in support design and excavation - support procedures.