1. Some species of herbaceous and semiwoody weeds, shrubs, and trees were sprayed with 1000-2000 p.p.m, aqueous solutions of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,,4,5-T) under warm humid Hawaiian conditions. In addition, several woody species were sprayed with 2.% concentrations of the chemicals in diesel oil. 2. When sprayed on species of herbaceous or semiwoody weeds, 2,4-D was either greater than, or equal to, 2,4,5-T in toxicity in aqueous solution at 1000 p.p.m. 3. When tested on some species of shrubs and trees, 2,4,5-T was observed to be more toxic than 2,4-D. Woody species, such as eucalyptus (Eucalyptus citriodora), popolo (Solarium nodiflorum), sensitive plant (Mimosa pudica), Christmas berry (Schinus terebinthifolius), lantana (Lantana camara), false ironwood (Casuarina equisctifolia), algaroba (Prosopis chilensis), Java plum (Eugenia jambolana), and cat's-claw (Caesalpinia sepiaria) were more injured by 2,4,5-T treatment. The guava (Psidium guajava) was and exception, being damaged more by 2,4-D than by 2,4,5-T. 4. Eucalyptus was killed with one spraying of 1000 p.p.m, of 2,4,5-T, while the same concentration of 2,4-D did little damage. The specificity of 2,4, 5-T for this species was further demonstrated with mature trees, 40-50 feet tall, when girdled trees were killed in (6 months after 2,4,5-T was applied to the wounds, while plants treated with 2,4-D were alive 20 months after treatment. 5. With the exception of lantana, which proved to be one of the most difficult species to control, 2.0% solutions of 2, 4-D and 2,4,5-T in diesel oil proved to be equal in toxicity to several woody species tested. Although the specificity of 2,4,5-T for eucalyptus was not in evidence at this high concentration, lantana was destroyed with one spraying of 2,4,5-T while 2,4-D-treated plants required repeated sprayings for control. 6. When sprayed on 8-month-old, actively growing pineapple plants, ammonium 2,4,5-T in aqueous solution at 2000-10,000 p.p.m. proved practically 100% toxic, while similar solutions of 2,4-D possessed much lower toxicity. In these tests 2,4,5-T was approximately twice as toxic as 2,4-D, but the damage produced by both compounds precludes their use as herbicidal sprays in fields of growing pineapples.