 Two hundred-sixty children with clinically diagnosed pulmonary TB including at least 100 HIV infected children from the Hospital del Nino, Lima, Peru, and 260 age-matched controls will be enrolled in this study. Mtb will be detected in NPAs and stool by new and traditional culture methods and by N2 PCR. Gastric aspirates from children with a clinical diagnosis of TB will also be tested. Children with a positive N2 PCR but without clinical evidence of TB requiring antituberculous therapy will be followed longitudinally. 