Simplified formulae are given for computing type I and type II error probabilities in a two stress level accelerated lif test plan developed by Yum and Kim(1990)Using the new formulae, some acceptance sampling plans for the mean value of anexponential distribution, based on type II censored data, are obtained. The criterion for choosing the censoring numbers, r1and rh,corresponding to a pair of higher-than-normal-use stress levels, is to minimize the sum, r1+rh.An approximate procedure is also included