Since the formulation of the national drug information network in 1975 in the United Kingdom, a work-sharing system was developed involving regional drug information centers. The designated file holder develops an in-depth, readily accessible data base which is used for the provision of information and advice to the drug information network. A specialist file was developed on drugs in breast milk. In 1977, the Trent and West Midlands drug information services, which had independently formed substantial data banks agreed to cooperate on the development of this file; DIDMIS (Drugs and Breast Milk Information Service) was then established. There are approximately 120 drug information centers. Data on excretion of drugs into breast milk form the major part of the file, but diagnostic agents, enviromental pollutants, alchol, and smoking are also included. The effects of drugs on milk content and production are also covered. Material relating to breast feeding, milk banks, and the presence of endogenous substances such as iron, immunoglobulins, and thyroxine, forms a smaller part of the file, The data bank covers both published and unpublishedmaterial in a variety of forms. At present, DIDMIS has manually operated card index retrieval system covering some 1500 entries. With the acquisition of microcomputers and data base management systems, it is hoped that file management time and response time will be reduced. The functions of DIBMIS are: 1)data collection and organization; 2)provision of a query answering service to health care professionals; 3)publication of active information; 4)formation of linds with other individuals or organizations; 5)stimulation of studies and research; and 6)establishment of criteria for evaluating studies and the formation of advice.