In a case-contact investigation of a patient (A) with smear- and culture-positive pulmonary tuberculosis, we found that co-workers in one room of a furniture factory had a higher prevalence of significant reactions to 5 Tu PPD tuberculin than other furniture factory workers. One co-worker also had active pulmonary tuberculosis. It was concluded that Patient A probably transmitted mycobacteria in a well-ventilated, spacious work setting; and that Patient A's disease and the subsequent outbreak could have been prevented.