Annual bluegrass has long been considered a troublesome weed on golf courses world- wide.  In warm-season turfgrass grown in the transition zone, glyphosate is used to control annual bluegrass during winter dormancy.  In 2006, extension personnel at the University of Missouri were called to the Country Club of Missouri in Columbia, MO to evaluate a dormant zoysiagrass fairway where glyphosate applied at 0.8 kg ae/ha failed to control annual bluegrass.  Suspected glyphosate resistant annual bluegrass plants were collected from the golf course and known susceptible annual bluegrass plants were collected the University of Missouri South Farm in Columbia, MO.  Both suspected glyphosate resistant and susceptible annual bluegrass plants were grown in a greenhouse in Columbia, MO and seed were collected.  Two greenhouse assays were preformed in the spring of 2007 from plants grown from the harvested seeds.  In the first trial, suspected glyphosate resistant annual bluegrass were controlled 15% with glyphosate at 0.8 kg ae/ha 16 days after treatment (DAT).  In the second trial, suspected glyphosate resistant annual bluegrass were controlled 68% with glyphosate at 0.8 kg ae/ha 21 DAT.   Conversely, susceptible annual bluegrass was controlled 91% and 100% with the same treatments.  In field studies in the spring of 2006 at the Country Club of Missouri, glyphosate applied at 0.8 kg ae/ha controlled annual bluegrass 30% at 61 DAT.  Acceptable annual bluegrass control (>97%) was achieved with glyphosate at rates > 3.2 kg ae/ha at 61 DAT.  Although glyphosate resistance is not yet confirmed in annual bluegrass, it is highly suspected.  Further studies are underway to elucidate the level of resistance and the resistance mechanism in suspected resistant annual bluegrass plants.