An investigation was carried out to establish the extent of drug resistance among treated patients. A sample population of patients living in Lahore, Pakistan, which is a high prevalence area for tuberculosis, was studied. The total of 256 culture-positive cases in this study were divided into three groups according to the length of previous treatment. There was no significant difference in the antituberculosis treatment regimens or the drug resistance pattern among the three groups. All the patients had had at least three drugs for more than 6 months, and streptomycin and isoniazid were always included in the regimen. About one-third of the patients showed resistance to one or more drug, with the highest resistance being to streptomycin and INH. Resistance to rifampicin, which was introduced fairly recently in this area, was a little more than 5%, which is an increase from the last report.