The OH radical initiated oxidation of 1,3-butadiene was studied under high NOx conditions by the LP-LIF method. We report a rate constant of (7.0 +/- 0.3) x 10(-11) s(-1) molecule(-1) cm(3) for OH addition to 1,3-butadiene which agrees well with values reported previously. Based on the analysis of OH cycling data combined with results of earlier isomeric selective studies, we have determined a branching ratio for the major hydroxy alkyl channel to be 0.87 +/- 0.08. Using this branching ratio, we have predicted the end product distribution for OH radical initiated oxidation of 1,3-butadiene and provide a condensed chemical mechanism. This study synthesizes previous work on OH initiated1,3-butadiene oxidation under high NOx conditions. (C) 2010 Elsevier B.V. All rights reserved.