Two field experiments (plant and ratoon crops) were conducted at Vega Baja and Barceloneta Land Authority pineapple farms in 1990 and 1991 to evaluate two grass herbicides. Fluazifop-p-butyl at 0.28 and 0.56 kg ai/ha and quizalofop at 0.224 and 0.448 ai/ha were applied postemergence twice to the 12-month-old plant crop and twice to 30-month-old ratoon pineapple plants. Two methods of application (over the top and directed spray) were used. Both herbicides gave excellent control of all grasses with no apparent crop injury. In the plant crop experiment, the highest fruit yield was obtained with quizalofop at 0.224 kg ai/ha applied over the top (69,289 kg/ha). This treatment differed significantly in yield with three of the other herbicide treatments. In the ratoon crop experiment, the highest pineapple yield was obtained with fluazifop-p-butyl at 0.56 kg ai/ha applied as directed spray (51,585 kg/ha). This treatment did not differ significantly with all other treatments.