National Health Service (NHS) Direct is a 24-h patient-led telephone advice service, based in England and Wales, which aims to help callers self-manage problems and reduce unnecessary demands on other NHS provision. Despite its rapid expansion as a source of health information and advice, little empirical work has investigated its impact and effectiveness. This paper reports on a study that aimed to evaluate the contribution of NHS Direct to the quality of care and its impact on health services within one part of the United Kingdom (UK). A postal survey of callers who had contacted NHS Direct between June 2004 and January 2005 with abdominal pain or cough and/or sore throat was conducted. Of 268 callers, over 90% reported they had followed the advice given by NHS Direct to self-care or to contact another health service. Fifty-one of the callers were referred to an Accident and Emergency department and, of these, 39 (76%) received a prescription and 20 (39%) were admitted to hospital. One hundred and forty-four callers were referred to a General Practitioner (GP) and, of these, 88 (61%) received a prescription and 21 (15%) were admitted to hospital. Of the 69 callers advised to self-care, 47 (68%) reported that they did not receive any further intervention while 18 (26%) reported they had subsequently contacted a GP and been given a prescription for medication. The paper concludes that most referrals made by NHS Direct to another health service were justified by the interventions received by patients. However a significant minority (26%) of callers referred to GPs did not receive any further intervention and there was some duplication of service use. Health professionals need to be aware that patients might have previously contacted another health service and provide advice on effective use of services.