The Longitudinal Dental Treatment dataset traces the National Health Service (NHS) primary care dental treatments for a c.5% cohort of patients treated in England and Wales between 1990 and 2006. The dataset is intended to be used primarily as a resource for academic research. The dataset was originally developed by NHS Dental Services, now part of the NHS Business Services Authority (NHSBSA), but has since been transferred to the Information Centre for Health and Social Care (HSCIC). This cohort study ceased collection of data in 2006 with the introduction of the 2006 NHS Dental Contract. The 2006 contract required a different national minimum dataset and there is currently no ongoing data collection for the original cohort of this study, nor any current plans for a similar exercise. Data formats: Users should note that due to the size of the data files, only SPSS and ASCII .dat versions are available; Stata versions have not been created. The longitudinal file data are contained in three files as follows: GDS Claims – contains a record for each claim. The file includes relevant information about the dentist and the patient, at the time of the course of treatment to which the claim relates, plus the dates of start and end of the course of treatment, where the surgery was located, and how much the course of treatment cost in gross fees (inclusive of any contribution from the patient). GDS Treats – contains a record for each treatment item on each claim, excluding those which are tooth-specific. Includes records of individual treatment items coded as in the Statement of Dental Remuneration. Against each treatment item is recorded a count of the number of instances (e.g. number of radiographs, number of visits).GDS Patts.sav – contains a record for each tooth-specific item on each claim, giving the tooth positions of each tooth treated. The data are restricted to those treatment items for which a tooth notation is required. For each treatment it records the teeth treated, using the characters #, %, £ and ‘ to designate the four quadrants - Upper Right, Upper Left, Lower Right and Lower Left respectively, and the numbers 1-8 and ABCDE and S (for supernumerary). There is also a record of the number of quadrants in which teeth were treated. Within the 40-character variable for tooth notation, the 1st, 11th, 21st and 31st are occupied by quadrant designators, each followed by the corresponding tooth numbers within the quadrant.