Objectives-To observe one general practice's attempt to reduce prescribing costs on becoming third wave fundholders through the introduction of a generic formulary applied to all new and repeat prescribing. To assess the impact on patients and prescribing patterns. Design-An observational study using interviews with patients and practitioners; questionnaires for patients and prescribing data. Setting-One urban general practice with five partners in Scotland. It became fundholding in April 1993. Subjects-71 searches of the register of repeat prescriptions identified 1274 potential changes in drugs. Questionnaires were sent to a stratified random sample of 280 patients four months after the changes were made; 33 interviews were conducted with 17 patients selected by local pharmacists to represent a wide range of opinion. Main outcome measures-Changes in prescribing and response and satisfaction of patients. Results-Of intended changes, 129 (70%) were in place after four months. Thirty three (20%) of the 167 patients who returned questionnaires were ''very unhappy,'' though interviews suggested that this was primarily with the communication they received rather than the change itself. Generic prescribing rose from one in three (37%) to over a half (58%). The volume of treatment dispensed (as treatment days) fell by 67 674 (10.7%), and the average cost per day's treatment fell by 3.1p from 32.3p per day in 1992 (9.4%), producing a total absolute saving of 24% (pound 137 712) over the first year. Conclusion-This practice has achieved a large reduction in prescribing costs rapidly. These were tolerated by patients, none of whom is thought to have left the practice for this reason. Great care must be taken to inform patients appropriately.