Data is a valuable resource in the NHS. Careful study of the statistics of disease and mortality can lead to understanding that saves lives - like the understanding that smoking cigarettes can cause lung cancer. Data relating to hospital episodes has been collected and studied for many years. The new "Care.Data" program is intended to allow data held at GP surgeries to be studied in a similar way. Data is to be anonymised and linked to hospital and other medical data and permission is given for this on a project by project basis. The original program was to have been started this year., but elicited a wave of public protest and was postponed by six months. Concerns centred on mistrust of the anonymisation and data storage, inadequacy of the explanatory information available to the public, concern about possible misuse by private purchasers of the data. .. Now Care.Data supremo Tim Kelsey has announced that the Care.Data project will be piloted at 500 surgeries. Measures to assure the independence of scrutiny of release of anonymised linked data are before Parliament. This is an important project for the NHS so public trust must be retained and regained. The careful roll-out proposed is a good start.