Current nude mice islet transplantation studies cannot be used prospectively. Therefore, to predict transplantation outcomes, reliable and rapid assays for islet quality assessment are warranted. This study evaluated the predictive power of the porcine islet ATP content on the outcomes of islet transplantation in nude mice. Here, we report that the ATP measurement using a small number of handpicked islets with a diameter of 100 to 150 mum is a good predictor of islet graft efficacy in nude mice. Using receiver-operator characteristic analysis, the area under the curve of the ATP content using a small number of handpicked islets was 0.867 (95% confidence interval 0.744-0.989, P<0.001). The sensitivity and the specificity measured were 83.3% and 73.3%, respectively. In conclusion, a simple and a rapid measurement of intraislet ATP content could be a promising substitute for current nude mice islet transplantation studies.