The management of a large-scale controlled clinical trial in the treatment of pulmonary tuberculosis includes the maintenance of accurate clerical procedures over a long period of time, both in the co-ordinating group and in the central laboratory responsible for the bacteriological investigations. Clerical procedures which are tedious and time-consuming, but nevertheless well defined, are, however, ideally suited to being transferred to a computer.In a current multi-centre co-operative controlled clinical trial of the treatment of tuberculosis in Britain computer methods are being applied in two main fields. First, the progress reports and the laboratory request forms which have to be completed in the treatment centres are being headed up specifically for each patient for each month using a Flexowriter (tape editing set). The report forms are sent from the co-ordinating group to the appropriate treatment centre with the following information already completed, the name and serial number of the patient, the treatment regimen, the date of start of treatment, the date of the next monthly appointment, and a detailed list of investigations to be undertaken at the attendance for the month in question. The necessary information is punched on paper tape computer output in a suitable format for printing on continuous forms by the Flexowriter. The second main computer application is in the central bacteriology laboratory. Each patient's basic data are stored in a magnetic tape file when the patient is admitted to the study, and results of all bacteriological examinations are also stored as soon as they become available. Thus all the information required to produce bacteriological reports for the treatment centres is readily accessible and reports are produced automatically as paper tape output ready for printing on the Flexowriter. The calculations associated with the interpretation of tests of sensitivity of the tubercle bacilli to the antituberculosis drugs are also being done by computer.The use of the computer has led to the more accurate performance of the set clerical procedures. It has also effected a considerable saving of the laboratory's technical staff time and of clerical staff time, and a lesser saving of medical, statistical and secretarial staff time in the co-ordinating group.