Annual bluegrass (Poa annua L.) is an invasive and widespread pest of highly managed turfgrasses. Despite the name, annual bluegrass behaves in turfgrasses as a perennial. Effective control strategies require a postemergence herbicide to control established plants if a turf manager hopes to exclude annual bluegrass from the turf. Effective, postemergence herbicdes for annual bluegrass are few. Pendimethalin () is a preemergence herbicide that controls many annual grasses as they germinate. We observed some postemergence activity on annual bluegrass when pendimethalin was applied in the fall. This research project sought to maximize the activity of pendimethalin for the postemergence control of annual bluegrass in Kentucky bluegrass turf. Pendimethalin was applied at rates of 0.84 to 5.0 kg ai/Ha to Kentucky bluegrass infested with annual bluegrass in the fall of 2003 and 2004. Different fromulations, application frequencies, and application timings were also investigated. Granular formulations of pendimethalin showed no postemergence activity indicating that foliar absorption is necessary for postemergence activity. Three fall applications of pendimethalin at 3.4 kg ai/ha/application gave 85+ % control annual bluegrass in both years of the trials.