Early bactericidal activity studies measure the ability of antituberculosis treatments to reduce the burden of Mycobacterium tuberculosis in sputum specimens collected overnight from smear-positive pulmonary tuberculosis patients during the first 14 days of therapy. This confirms the efficacy of novel agents or drug combinations in human patients, allows comparison of different drug dosages and a preliminary assessment of the drugs' pharmacokinetics and toxicity in closely observed patients. In the past few years several novel antituberculosis agents have demonstrated significant early bactericidal activity and progressed to studies of longer duration. Most recently the early bactericidal activity of drug combinations was found to be similar to results predicted by murine studies. This may contribute to expediting the future progress of drug evaluation.