Patients receive up to 8 weeks of two or more anti-tuberculosis drugs, of which at least two are isoniazid, rifampin, pyrazinamide, or ethambutol. Blood specimens are collected at 2, 6, and 10 hours after administration of study medication, once between Days 10 and 14 of a phase of daily treatment and once while on an intermittent dose regimen (twice weekly or three times weekly).