The sensitivity of the prenalterol test has been evaluated in 21 patients with pseudoischaemic T waves and no documented organic heart disease. The sensitivity of the test (40 micrograms/kg i.v. in 3 min) was 90.4%. In comparison, the isoproterenol test, performed in 10 of these patients, showed a similar sensitivity but prenalterol had a lower positive chronotropic effect than isoproterenol (p less than 0.0005). The possible advantages of the introduction of the prenalterol test in clinical practice are analysed.