A test reordering algorithm is presented to improve the results of scan chain diagnosis when a limited amount of fail data is collected by the tester. Tests are reordered based on information derived by applying an enhanced defect diagnosis procedure to the faulty units with scan defects. Tests that are found important for diagnosis of more faulty units are placed earlier in the test set based on the expectation that these tests will be useful for diagnosis of other faulty units as well. Experimental results collected for benchmark circuits in the presence of single and multiple scan chain defects indicate that reordering tests based on diagnostic information improves the quality of scan chain diagnosis when a limited amount of fail data is collected by the tester.