Physiological measures were recorded during repeated PDD tests to determine whether reaction levels change with test repetition. Two groups of 22 healthy male subjects completed six peak-of-tension PDD tests on each of two test days. A minimum between test day interval of 6 days was maintained. The treatment group was programmed to respond deceptively to one of seven test questions, and the control group was programmed to respond truthfully to all questions. The respiration and galvanic skin resistance (GSR) line lengths, GSR peak response amplitude and latency, and cardiovascular inter-beat-interval (IBI) were calculated for each response. Analyses showed that, except for GSR peak response latency, differential physiological reactivity during a PDD test did not change significantly over repeated tests or days; there was a decrease in average respiration line- lengths at the initial tests of each day; and differential changes in average respiration line-length, GSR peak latency, and cardiovascular IBI responses corresponded to deception. Power analyses were calculated to assist in result interpretation. The study suggests that PDD decision accuracy concerning subject truthfulness should not decrease during repeated testing. 2 figures and 44 references