Field studies were conducted in Virginia and New Jersey from 2010 to 2011 to evaluate the use of methiozolin for annual bluegrass control in creeping bentgrass putting greens. In Virginia, non-replicated demonstrations were established on four different putting greens at two golf courses. At Spotswood Country Club (CC), three strips (2m by 25m) were treated with methiozolin at 0.75, 1.5, and 3.0 kg ai/ha on March 18, April 15, and Oct 20, 2011.  At Lakeview CC, three different putting greens were treated with methiozolin at 1.0 kg/ha on April 15, May 13, and Oct 20, 2011.  Initial annual bluegrass populations were 40 to 60% cover at all locations.  When assessed in November 2011, annual bluegrass cover reduction was 20, 75, and 95% in plots treated with 0.75, 1.5, and 3.0 kg/ha methiozolin, respectively.  At Lakeview, annual bluegrass cover reduction was 90, 60, and 30% on the three test sites. In New Jersey, studies were established in the fall of 2010 at Riverton, Metedeconk, and Charleston Springs CC. Methiozolin treatment regimes were 0.5, 1.0 and 2.0 kg/ha applied twice in Sept/Oct, Oct/Nov, and once in Nov. Methiozolin at 0.5 and 1.0 kg/ha was also applied three times in Sept/Oct/Nov. Annual bluegrass populations were high at Riverton (> 50%), low at Charleston Springs (<10%) and initially low at Metedeconk. However, by late fall plots at Metedeconk averaged 30 to 40% annual bluegrass cover. Creeping bentgrass injury was not evident until the following March at all three locations.  At Charleston Springs, creeping bentgrass injury was 33 and 24% when methiozolin was applied at 2.0 kg/ha in Oct/Nov and Sept/Oct, respectively, but less than 10% with all other treatments. However, in late March creeping bentgrass injury increased to 65 and 30% with these two treatments. In addition, injury with all other treatments increased to 9 to 30%. At Metedeconck, creeping bentgrass injury was most evident in late March with 60 and 80% injury observed when methiozolin was applied at 2.0 kg/ha in Sept/Oct and Oct/Nov, respectively. Injury with other treatments ranged from 10 to 60%. At both locations, creeping bentgrass recovered rapidly with 30% injury or less with all treatments in early May. Many treatments which had shown noticeable injury in late March had completely recovered by early May. Annual bluegrass control was 85% or greater at both locations when methiozolin was applied at 1.0 kg/ha or greater regardless of application timing. Similar results were observed at Riverton CC when methiozolin was applied at 1.0 kg/ha or greater. These studies suggest that methiozolin can effectively reduce annual bluegrass populations dramatically when applied in the fall. However, additional research needs to be conducted to balance annual bluegrass control while limiting creeping bentgrass injury.