The complex physiology of orienteering performance is not well understood but recent advances in technology allow for more in-depth investigation. The purpose of this study was to develop and validate physiological field tests for elite orienteers in Australia. Seven male and three female elite orienteers volunteered to take part in the study. Subjects completed an incremental fixed-distance (803m) trial in Australian forest terrain, paced by a bicycle equipped with a speedometer. This was replicated in the laboratory using a 4.5% grade for treadmill running. Subjects also completed four (males) or three (females) laps of a 1340m terrain loop incorporating uphill, track and downhill sections. Subjects then repeated this test in the laboratory, with treadmill grade manipulated to replicate the gradient profile of each section. Heart rate (HR) and oxygen uptake (VCh) were recorded continuously with telemetry during each stage/lap. Blood [La] and RPE were recorded after each stage/lap. In the incremental tests, no significant differences (p=0.05 level) were observed in HR, VO2, blood [La] or RPE between the Field test, and its Laboratory replication over the entire range of speeds tested. The actual speeds run during the Field tests were significantly faster than the Laboratory test at the slowest speed (8 kmh- 1 ) attempted, and slower at the fastest speed (18 km-h-1) attempted. In the time-trial tests, no significant differences were observed in HR, VO2, blood [La] or RPE between the Field test and its Laboratory replication. The running speeds in the Field tests were significantly slower than the Laboratory tests. Running speed appeared inversely related to the course profile and the terrain also affected the speeds that could be achieved. Despite the changes in the course profile, the physiological responses to the course were maintained within a narrow range at a high level (-95% of maximal heart rate, 80-90% of VO2max, blood [La] -10 mM) for the duration of the 20-25 minute test. The Field tests that were developed in this study for elite orienteers in Australian forest terrain were successfully validated by replicating the protocols in a Laboratory setting.