Androgenic anabolic steroids (AAS) are often used by athletes to enhance athletic performance but are strongly associated with detrimental cardiovascular effects including sudden cardiac death. Hypothesis: AAS use increases myocardial susceptibility to ischaemia/reperfusion injury. Methods: Rats were trained (swimming) with or without intramuscular injection of nandrolone Iaurate (0.375 mg/kg). Untrained rats with or without nandrolone served as controls. Hearts were mounted on the Langendorff perfusion apparatus and mechanical function was measured before and after 20-min normothermic global ischaemia. Myocardial tissue samples were collected for determination of tissue cyclic nucleotide and TNFa concentrations. Results: Anabolic steroids decreased the rate pressure product (RPP) of the exercise-trained rat heart [34 582 ᠱ778 mmHg/min vs 28 868 ᠲ 446 mmHg/min for exercise-trained steroid-treated hearts (p < 0.05)]. Reperfusion RPP was lower in both the sedentary, and the exercise-trained, steroid-treated hearts than in their concurrent vehicle-treated controls (18 276 ᠲ 026 mmHg/min vs 12 018 ᠱ 725 mmHg/min for sedentary steroid-treated hearts and, 21 892 ᠲ 912 mmHg vs 12 838 ᠱ 536 mmHg/min for exercise-trained steroid-treated hearts). Myocardial TNFa [267.75 ᠴ4.25 pg/g vs 190.00 ᠱ5.75 pg/g (p < 0.05)] and cAMP concentrations [406.04 ᠱ8.41 pmol/g vs 235.6 ᠴ3.26 pmol/g (p < 0.05)] were elevated in the steroid-treated hearts when compared with their untreated counterparts. Conclusions: Supraphysiological doses of anabolic steroids, whether taken during exercise training or under sedentary conditions increase myocardial susceptibility to ischaemia/reperfusion injury in our model. This increased susceptibility may be related to steroid-induced increases in the pre-ischaemic myocardial cAMP concentrations and/or increases in both pre-ischaemic and reperfusion TNFa concentrations.