Grid applications of hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] pellets at 2.2 kg ai/ha or less did not effectively control honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell ♯3 PRCJG], blackbrush acacia (Acacia rigidula Benth. ♯ ACARI), lotebush condalia [Condalia obtusifolia (Hook.) Weberb. ♯ CNCOF], granjeno (Celtis pallida Torr. ♯ CETPA) or twisted acacia [Acacia tortuosa (L.) Willd.] growing as mixed stands on clay loam or clay soils. Efficacy of hexazinone apparently was affected little by variation in rainfall ranging from 35% less to 51% greater than the long-term average during the year of application. Apparent mortality of honey mesquite, granjeno, and lotebush condalia was increased by increasing the application rate from 2.2 to 4.5 kg/ha on clay loam soils. Control of honey mesquite, blackbrush acacia, and twisted acacia with 2.2 kg/ha was better when applied to sandy clay loam than to clay soils.