Unrecognized tuberculosis transmission outside the household has led to "micro-epidemics". We sought to evaluate how frequently locations outside the household were addressed in tuberculosis contact investigations, and to identify associated patient factors. We reviewed all tuberculosis patients reported in Montreal, Canada, during 1996-2004. Among this largely foreign-born patient population, investigation of locations outside the household was limited: there was documented attendance at 1 non-household location for 40% of the most contagious patients. Given complex, dispersed patterns of work, educational attendance, social activity, and transportation, contact investigation strategies may warrant reevaluation in large cities such as Montreal.