NHS Direct, a national telephone helpline for health advice, was established in 1998 to provide health information and advice to callers and refer them to an appropriate service. This article briefly describes the nature of the NHS Direct call record and discusses issues relevant to the use of the data for disease surveillance and epidemiological purposes. Clinical decision support software [the NHS Clinical Assessment System (NHS CAS)] is used by NHS Direct to collect callers' demographic details and direct them to the appropriate level of care. Data relating to NHS Direct calls provide a timely snapshot of symptoms occurring in the community and are summarized in 'off the shelf' NHS CAS reports. Adapting the system to provide customized data extracts requires considerable development work. When interpreting NHS Direct derived data, particular attention should be given to the age distribution of callers, NHS Direct demand surges, call 'networking' and changes to the NHS CAS clinical algorithms. An increasingly rich source of baseline data, growing body of published work, and a more 'bedded down' NHS Direct service will further our understanding and acceptance of the value of the NHS Direct call record.