The gas phase reaction of the hydroxyl radical with allene has been studied theoretically and experimentally in a continuous supersonic flow reactor over the range 50 <= T/K <= 224. This reaction has been found to exhibit a negative temperature dependence over the entire temperature range investigated, varying between (0.75 and 5.0) x 10(-11) cm(3) molecule(-1) s(-1). Product formation from the reaction of OH and OD radicals with allene (C3H4) has been investigated in a fast flow reactor through time-of-flight mass spectrometry, at pressures between 0.8 and 2.4 Torr. The branching ratios for adduct formation (C3H4OH) in this pressure range are found to be equal to 34 +/- 16% and 48 +/- 16% for the OH and OD + allene reactions, respectively, the only other channel being the formation of CH3 or CH2D + H2CCO (ketene). Moreover, the rate constant for the OD + C3H4 reaction is also found to be 1.4 times faster than the rate constant for the OH + C3H4 reaction at 1.5 Torr and at 298 K. The experimental results and implications for atmospheric chemistry have been rationalized by quantum chemical and RRKM calculations.