Isocitrate lyase (ICL) catalyses the first step of the glyoxylate bypass pathway, which reversibly cleaves isocitrate into succinate and glyoxylate. This pathway occurs in a wide range of pathogens and plays a key role in the pathogenesis of Mycobacterium tuberculosis (MTB) suggesting that it may represent a drug target for the treatment of tuberculosis. ICL was cloned, expressed, and purified, and a high-throughput screen (HTS) developed to screen active extracts derived from traditional Chinese medicines (TCMs) for inhibition of ICL. A colorimetric assay based on the formation of glyoxylatephenylhydrazone was used to measure ICL activity. The assay had signal to noise (S/N) of 12.74 and Z' factor of 0.72, indicating that the assay was suitable for HTS. Screening of a collection of 465 extracts derived from TCMs resulted in the identification of two extracts from Illicium verum Hook.f (Illiciaceae, XHD-1) and Zingiber officinale Rosc (Zingiberaceae, XHD-2), which inhibited ICL with IC 50 values of 47.7716.9 and 18.270.9 mg/ml, respectively. Drug Dev. Res. 67:818-823, 2006.