The helpfulness of technological tests in the diagnosis of diseases presenting as jaundice was examined using a measure of expected utility derived from decision theory. Data from 243 patients admitted with jaundice yielded a total of 2260 test-results from twenty seven tests used. The results were partitioned into a total of 123 bands. Forty-three bands had a sufficient number of results to be considered for calculation. Eleven out of the 27 tests and 16 of 123 bands gave information recognized to be worthwhile. They contributed to the diagnosis of the 7 commonest diseases, and would permit the selection of the best combination of tests to be performed. The frequency of use of tests did not reflect their utility. A test-sequencing proforma might be a useful aid in the work-up of patients.