Nineteen previously trained resident anaesthetists were instructed to perform adult single-rescuer basic life support for 5 min on a manikin, in a double-blind crossover design, changing the hand of contact with the sternum from right to left while performing external cardiac compression (ECC). Total, correct and incorrect ECCs comprising of inadequate depth, wrong hand placement, incomplete relaxation and too much compression were recorded and grouped according to the dominant hand (group DH) or non-dominant hand (group NH) in contact with the sternum. The number of correct ECCs was significantly greater in group DH, median 141 compared to group NH, median 97; P < 0.005. More ECCs were of inadequate depth in group NH, median 34 as compared to a median of 8 in group DH; P < 0.005. Similarly, the incidence of wrong hand placement was significantly higher in group NH; median of 4 versus median of 0 in group DH, P < 0.05. The incidence of incomplete relaxation and too much ECC was not significantly different between the two groups (P < 0.05). We conclude that ECC is performed with fewer errors when the dominant hand of the rescuer is placed in contact with the sternum.