The mycobacterial antigen MPB-64 was formulated for delivery in a transdermal patch and used as a diagnostic skin test reagent to detect active tuberculosis (TB) in patients attending a clinic in Manila, The Philippines. The MPB-64 Transdermal Patch was applied to 62 patients, 49 with sputum-positive active disease and 13 who had completed TB chemotherapy, and to 28 non-TB but tuberculin-positive controls. The results were read at 72 h. The sensitivity of the Transdermal Patch was 87.8%, with an efficacy of 92.9% and a specificity of 100%. The 13 TB patients who had completed 6 months of TB chemotherapy showed different reactions to the MPB64 patch test: those who had completed chemotherapy < 4 months before testing were positive; 50% of patients who completed chemotherapy 5 months previously were positive; and those who had completed chemotherapy 7 and 8 months before were negative. All the non-TB controls with positive tuberculin tests were negative to the MPB-64 Transdermal Patch, even at the highest protein dose tested. This test may be a useful method to distinguish active TB patients from TB-infected but asymptomatic individuals. Moreover, the MPB64 Transdermal Patch may be useful to monitor successful chemotherapy.