In the pulse radiolysis of concentrated sulfuric acid solutions, the absorption spectrum and the molar absorption coefficient (1600 dm³ mol^–1 cm^–1) of the sulfate radical are unchanged up to 10 mol dm^–3 H₂SO₄, suggesting that the sulfate radical exists in the dissociated form (SO^–₄). Two formation processes for the sulfate radical have been directly demonstrated in sulfuric acid and hydrogensulfate solutions: a fast one completed in the duration of the electron pulse, and a slow one occurring over a microsecond time range. For sulfate solutions only the fast formation process is observed. In sulfuric acid solutions the slow formation process is OH + HSO^–₄→ H₂O + SO^–₄(4.7 × 10⁵ dm³ mol^–1 s^–1) and OH + H₂SO₄→ HSO₄+ H₂O → SO^–₄+ H₃O⁺(1.4 × 10⁷ dm³ mol^–1 s^–1), and the fast formation process is the direct action of radiation on sulfuric acid with a G value of (2.7 ± 0.4)× 10^–2 molecule eV^–1. The yields of (OH + SO^–₄) and H can be quantified as: G(OH + SO^–₄)= 2.9f_w+ 2.7f_s and G(H)= 3.7f_w+ 2.7f_s. The yields of SO^–₄ have also been evaluated and the decay kinetics and reactions of the sulfate radical studied.