A project in the late 1980s evaluated the different methods of case identification in remote rural communities in Guerrero. The diagnoses made by medically trained personnel (usually recent medical school graduates, called pasantes, performing their mandatory period of service in rural areas) were compared with those of local volunteers with only brief training. Both these methods compared favourably with the existing system of passive surveillance based on voluntary attendance at health centres. Quality control was studied in 94 health centres that send sputum samples to state laboratories; no false positives or false negatives were found among samples analyzed by voluntary promoters or pasantes. The cost, the number of positive diagnoses and efficiency of each method was measured and compared. It was shown that, where voluntary promoters take part in the surveillance, cases were diagnosed earlier in life and a greater number of cases were found. The cost of diagnosing a case of TB by voluntary promoters proved to be three times less than by thepasantes. A further survey of students in the University’s Schools of Medicine and Chemical Sciences illustrated that their knowledge of and attitude towards the diagnosis of tuberculosis by baciloscopy was strongly conditioned by their undergraduate training.