Annual bluegrass (Poa annua L.) is an invasive weed in golf course fairways and tees. Golf course managers typically apply plant growth regulators (PGRs) like flurprimidol (FL) to these areas to manage clipping production, improve turf color or density and minimize annual bluegrass encroachment. This two-year field study evaluated the effects various FL, trinexepac-ethyl (TE) and FL + TE tank-mix combinations when applied monthly to a mature creeping bentgrass (Agrostis stolonifera Huds. Farw. ‘L-93’) research fairway. Prior to applications there was approximately 30-40% annual bluegrass mixed in the bentgrass fairway. Turfgrass appearance which included  color and density, and percentage annual bluegrass were visually rated on a regular basis throughout each growing season. After two consecutive years of PGR applications the most effective treatments for reducing annual bluegrass populations were FL (0.28, or 0.56 kg a.i. ha^-1) or FL + TE (0.56 + 0.06 kg a.i. ha^-1) which resulted in 8.3, 8.5 and 4.0 % annual bluegrass, compared to 25.8 % in the untreated plots. In general PGR applications improved turfgrass quality ratings. Among PGR treatments, however, the FL (0.56 kg a.i. ha^-1) and the FL + TE (0.56 + 0.06 kg a.i. ha^-1) tank-mix caused some temporary turf discoloration for the Oct. application in year one which coincided with the first frost of the season. This study indicates that even where rather large, 25-30%, annual bluegrass populations exist, regular FL applications during the growing season can effectively increase bentgrass resulting in higher turfgrass quality and improved fairway conditions.