An audit of a rural practice's use of laboratory investigations, over a period of three months, 3,4 in that as well as calculating costs an attempt has been made to assess the effectiveness of the investigations' results in relation to subsequent decisions concerning patient management. Two principals and a trainee were involved in the project, in a practice with a list of 3,200 patients. Approximately 12% of patients contacts were investigated which is comparable with previous studies 3, 4, 5. Cervical cytology and pregnosticon testing were excluded from the study. A total of 594 investigations were requested from 421 patients. Microbiology accounted for 39.8% of the total requests, Haematology 31.3%6, Biochemistry 22.4% and Radiology 6.5%. These results are similar to other published studies, though, requests for Radiological were somewhat lower 3, 4, 5, 7. An estimate of the annual cost of investigations is given (see Tables I-IV). Implications of the results for the practice in cost terms is discussed.