We aimed to determine whether an Ironman distance triathlon resulted in sustained myocardial injury detected by electrocardiography, biochemical markers or echocardiographic assessment of left ventricular systolic and diastolic function. Electrocardiograms, blood for analysis of creatine kinase (CK) and its MB fraction, cardiac troponin I (cTnI) and echocardiograms were obtained in 15 male athletes prior to and at a mean of 4.7 days after competing in the Australian Ironman Triathlon. Regional wall motion scores, left ventricular ejection fraction (LVEF) and mitral inflow parameters were determined from the echocardiograms by a blinded investigator. Levels of cTnI were undetectable in all athletes and total CK was mildly elevated in 7/15 athletes prior to the event. Baseline wall motion, ejection fraction and diastolic filling were normal in all athletes. CK levels were increased post-race (p < 0.05) with a mean post-race level of 451U/l. Levels of cTnI were undetectable post-race in 14 athletes with a level of 0.9 microg/l recorded in one athlete, although all were within the laboratory's normal range for the assay. Mitral inflow parameters and LVEF did not change post-race and regional wall motion was normal in 14 of 15 athletes. Regional wall motion abnormalities detected in 1 athlete had resolved by 25 days post-race. These findings indicate that ultraendurance exercise does not result in sustained myocardial injury in this group of elite athletes.