Using electronic absorption spectra and thin layer chromatography, the reaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH) with O 2•-, HO • , HO -, and HOO -anions and free radicals revealed the formation of the para-nitro-and para-hydroxy-derivatives of 2,2-diphenyl-1-picrylhydrazine (DPPH-H) and of DPPH fragmentation products (diphenylamine, tetraphenylhydrazine). The reaction of DPPH with the O 2 •-anion-radical (from KO 2 in benzene solution at room temperature in the presence of 18-crown-6 ether) is pseudo-first-order during the first 25 minutes.