AbstractMycobacterium tuberculosis is a serious worldwide health threat, killing almost 2 million people per year. Alternative antimycobacterial drugs are urgently needed; studies have shown that medicinal plants traditionally used to treat respiratory diseases are a potential source of compounds to treat tuberculosis. This paper studied the antimycobacterial activity of 28 extracts from four different plant species that have been used in traditional Mexican medicine to treat tuberculosis. Bark and leaf crude extracts of Juglans regia L., Juglans mollis Engelm., Carya illinoensis (Wangenh) K. Koch and Bocconia frutescens showed in vitro anti‐M. tuberculosis activity. Hexane bark extracts from C. illinoensis, J. mollis and J. regia were the most active with a minimal inhibitory concentration (MIC) of 31, 50 and 100 µg/mL, respectively. Ethanol bark extracts from C. illinoensis and J. mollis showed activity at 100 and 125 µg/mL, respectively. Leaf extracts had the lowest activity. Methanol and hexane leaves extracts from B. frutescens had a MIC of 125 µg/mL. None of the aqueous extracts showed antimycobacterial activity. Copyright © 2008 John Wiley & Sons, Ltd.