GH2 was determined in neutral and in 1 M NaOH air-saturated solutions as a function of [N3-]. It was found that N3- reduces GH2 from 0.43 at 10-3 M N3- to 0.157 at 5 M N3- in neutral solutions and from 0.37 at 0.5 M N3- to 0.21 at 4 M N3- in alkaline solutions. Through pulse radiolysis studies it was found that the value of the rate constant keaq+N3- was ≤ 1.5 × 106 M-1 sec-1 and that N3- had no effect on Geaq. In competition experiments between N3- and isopropyl alcohol, kH+N3- = 2.7 × 109 M-1 sec-1 was obtained. From the decrease of GH2 by efficient electron scavengers it was concluded that the reaction H + eaq → H2 + OH- in spurs makes a major contribution to GH2. This conclusion together with other experimental results makes necessary the assumption that in addition to a distribution in the number of radicals in various spurs there is a distribution of concentrations of radicals in each kind of spur. The "condensed spurs" (spurs with higher initial concentration of radicals) have an important contribution to GH2.