Helicobacter pylori (HP) infection can cause hypochlorhydria, a positive risk factor for Mycobacterium tuberculosis (MTB) infection. This study examined the association between HP and MTB infections among persons attending the Policlínico Peruano Japonés Gastrointestinal Clinic in Lima, Peru. From 23 June 2000 to 18 August 2000, consenting 18-55 year olds who attended the clinic for gastric biopsy gave blood for HP serologic testing, underwent tuberculin skin testing (TST) and completed a social and medical history. Of 128 participating patients, 78 (61%) were TST positive for MTB, and 107 (84%) were infected with HP by serology. Of the patients who were HP positive, 67 (63%) developed positive TST reactions compared to 11 (52%) of 21 HP-seronegative subjects (OR 1.29; 95% CI 0.54-3.11; P=0.6). There was no association after adjusting for covariates of H. pylori infection (OR 0.78; 95% CI 0.23-2.71; P=0.7). However, study power was limited by high prevalence of the two infections.