The ability of fourteen competitive helmsmen of different skill levels to sail a standard course towards the wind (upwind) was assessed using a virtual reality sailing simulator. The simulator consisted of a Laser dinghy deck which pivoted between two supports and was dynamically controlled by a computer driven pneumatic ram. Computer generated graphics realistically reproduced helming, sheeting, tacking and boat trim. After familiarisation with the simulator, subjects performed a standard 1 km upwind test and were ranked according to their completion time. The subjects were then asked to fill out a questionnaire to obtain an estimate of how effectively the simulator reproduced the conditions of actual sailing. Mean scores showed the sailors considered overall feel and simulation of physical movement as "good" (5 on a scale of 1 to 6). Rankings for the upwind test were compared with independent competition rankings for each subject. Overall time to complete the upwind test correlated well with a subject's external ranking (Spearman's rank order r=0.99). The results indicate that the test used can differentiate between variations in upwind sailing performance over a wide range of ability. The simulator thus provides for the first time a method of measuring and analysing a sailor's performance in a controlled laboratory setting.