Genes encoding defense-related proteins have been used to alter the resistance of plants to pathogens and other environmental challenges, but no single fungal gene overexpression has produced broad-spectrum stress resistance in transgenic lines. We have generated transgenic tobacco (Nicotiana tabacum) lines that overexpress the endochitinases CHIT33 and CHIT42 from the mycoparasitic fungus Trichoderma harzianum and have evaluated their tolerance to biotic and abiotic stress. Both CHIT33 and CHIT42, individually, conferred broad resistance to fungal and bacterial pathogens, salinity, and heavy metals. Such broad-range protective effects came off with no obvious detrimental effect on the growth of tobacco plants.This work was supported by grants from the Spanish Ministerio de Educación y Ciencia and the Dirección General de Universidades e Investigación of the Junta de Andalucía, Spain. M.d.l.M.D. was the recipient of a postgraduate fellowship from the Ministerio de Educación y Ciencia. B.C. is a fellow of Programa Averroes, Junta de Andalucía, Spain.Peer reviewed