The detailed kinetics of the multistep mechanism of the Au^III ion reduction into gold clusters have been investigated by radiation chemistry methods in 2-propanol. In particular, a discussion on the steady state radiolysis dose-dependence of the yields concludes to a comproportionation reaction of nascent gold atoms Au0 with excess Au^III ions into Au^II and Au^I. This reaction should be achieved through Au^III consumption before the coalescence of atoms Au0 into gold clusters may occur. Then gold clusters catalyze the reduction of Au^I by 2-propanol. It was also found that a long-lived Au^II dimer, (Au^II)₂, was transiently formed according to the quantitative analysis of time-resolved absorbance signals obtained by pulse radiolysis. Then the disproportionation of Au^II is intramolecular in the dimer instead of intermolecular, as usually reported. The yields, reaction rate constants, time-resolved spectra, and molar extinction coefficients are reported for the successive one-electron reduction steps, involving especially the transient species, such as Au^II, (Au^II)₂, and Au^I. The processes are discussed in comparison with other solvents and other metal ions.