The photoionization (PI) cross sections of allyl and 2-propenyl radicals to form C3H5+ were measured using tunable vacuum ultraviolet (VUV) synchrotron radiation coupled with photofragment translational spectroscopy. At 10 eV, the cross sections were found to be 6.2 +/- 1.2 and 5.1 +/- 1.0 Mb, respectively. Using these values, the PI efficiency curves for each radical were placed on an absolute scale from 7.75 to 10.75 eV. (C) 2003 Elsevier B.V. All rights reserved.