In the UK National Health Service (NHS), NHS Direct, the national 24-h telephone helpline, has been available in England and Wales since 2000 and has been termed a 'single gateway' to health care. We conducted a population survey of 15,004 people in areas covered by the service, which included questions about NHS Direct use and socio-economic characteristics. After removing undeliverable questionnaires, the survey response rate was 60% (8750/14,516). In all, a quarter of respondents had ever used NHS Direct (26%, 95% confidence interval 25-27), ranging from 32% of the population in Preston/Chorley (888/2,794) and Newcastle and North Tyneside (515/1,621) to 17% (2,215/8,536) in Sheffield, which had introduced the service 20 months later. Logistic regression showed that those from poorer socioeconomic groups or with communication difficulties were less likely to have used the service than others. Overcoming this apparent bias against those likely to have the greatest need is an unsolved problem not confined to telemedicine.