Weed competition for nutrients and space is often detrimental to turfgrass establishment, making weed prevention a critical step to proper establishment.  Preemergence herbicides are often used for weed suppression during the establishment process.  Selective preemergence herbicides capable of being applied at the time of seeding have become available to the turfgrass industry in resent years.  The objective of this study was to evaluate the effects of various preemergence and postemergence herbicides on Digitaria sanguinalis L. (large crabgrass) during Poa pratensis L. (Kentucky bluegrass) establishment from seed.  Experimental design was a single factor (herbicide application) randomized complete block design.  Treatments included preemergence and postemergence herbicides, quinclorac, dithiopyr, mesotrione, and siduron in comparison to a control.  Preemergence herbicides, mesotrione and siduron, were applied the day of seedling.  Postemergence herbicides, quinclorac and dithiopyr, were applied 30 days after seeding.  Research was conducted on a native Owosso-Marlette sandy loam soil, seeded with large crabgrass 22 June 2004, renovated 24 May 2006, and seeded 30 May 2006 with a Kentucky bluegrass blend (25% Showcase, 25% Rugby II, 25% Midnight, and 25% P105).  Urea (46-0-0) was applied at a rate of 2.4 g N m^-2 on 14 June, 21 June, 28 June, and 5 July 2006, followed by 26-7-14 applied at a rate of 4.9 g N m^-2 on 19 July, and 9 August 2006.  Data collected included crabgrass percent coverage, Kentucky bluegrass coverage, and visual color ratings.  The preemergence herbicide, mesotrione provided the greatest large crabgrass suppression throughout the Kentucky bluegrass establishment period, up to 100% control 20 days after seeding.  Mesotione and dithiopyr applications provided 80 and 69%, respective reductions in crabgrass population, in comparison to the control observed 71 days after seeding.