Although ischaemic preconditioning (PC) has been shown to protect normal hearts from a subsequent ischaemic insult, its protective effect on the hypertrophied myocardium has not been widely studied. This study was designed to investigate whether ischaemic preconditioning protects hearts with hypertrophy (HYP). Cardiac HYP was produced in rats by suprarenal abdominal aortic constriction of 5 weeks' duration, and was defined as left ventricular weight: body weight [LVW: BW (mg/g)] ratio over 3.0. Isolated rat hearts were perfused with a modified Krebs-Henseleit buffer at 37 degrees C in a Langendorff preparation. Hearts from sham-operated animals (NORM) and those with HYP underwent a PC protocol consisting of 3 min of global zero flow ischaemia, 5 min of reperfusion followed by 5 min of ischaemia and 5 min of reperfusion. This was followed by 20 min ischaemia and 45 min reperfusion. Control hearts in the HYP and NORM groups were not subjected to the PC protocol. There were, thus, four experimental groups: NORM control (n = 9), NORM, PC (n = 9), HYP control (n = 9), HYP, PC (n = 11). The recovery of function after ischaemia was evaluated by recovery of left ventricular developed pressure (LVDP) expressed as % of the initial value (LVDP%). The LVW: BW ratio for the HYP groups was 3.4 (SEM 0.08). LVDP% was higher (p < 0.01) in preconditioned groups as compared with controls. In NORM control recovery was 49.3 (6.1), NORM, PC 76.5 (3.4), HYP control 39.8 (4.6) HYP, PC 70.1 (4.1). These data indicate that the ability of preconditioning to protect against ischaemic ventricular dysfunction is preserved in this model of cardiac hypertrophy.