Genes encoding acetohydroxyacid synthase were isolated from cotton, engineered to express an imidazolinone-resistant form of the enzyme and reintroduced into cotton utilizing an Agrobacterium mediated transformation system. Herbicide tolerant plants were regenerated and outcrossed with various breeding lines. Field trials were conducted with F2 progeny of a cross with El Dorado Acala to assess productivity (yield), fiber properties and herbicide tolerance versus the recurrent parent.