Individual general practitioners are known to vary widely in the number of patients they refer to hospital outpatient departments; indeed there is increasing concern that the 'high' referrers use a disproportionate quantity of National Health Service resources. Data from a one-week survey of referrals by 122 general practitioners in one health district showed that a different age-sex mix of patients consulting individual general practitioners might account for about one quarter of his or her referrals. The results also showed that different referral rates, calculated by using either workload or list size denominators, identified markedly different groups of high referrers. These different methods of measurement are discussed, and on practical grounds a referral rate based on actual referrals divided by mean practice list size is suggested for future comparisons.