The molar absorbances (epsilon) and the stability constants (beta) of the iron(III)-glyoxylate complexes were determined spectrophotometrically at 254 nn wavelength in aqueous acidic solutions. The molar absorbances (M-1 cm(-1)) of the complexes were at 254 mm: epsilon(1) = (3+/-1).10(3); epsilon(2) = 5180+/-150; epsilon(3) = 4050+/-200; epsilon(4) = 7870+/-80. The log(10)beta values of complexes computed at zero ionic strength were as follows: log(10)beta(1) = 3.10+/-0.30; log(10)beta(2) = 5.45+/-0.40; log(10)beta(3) = 6.20+/-0.30; log(10)beta(4) = 7.10+/-0.30. Based on the stability constants, molar absorbances and photochemical kinetics the individual quantum yields of the complexes were also determined: phi(1)(Fe(3+)Gl) = 0.13+/-0.04; phi(2)(Fe(3+)Gl(2)) = 0.31+/-0.10; phi(3)(Fe(3+)Gl(3))= 0.76+/-0.10; phi(4)(Fe(3+)Gl(4)) = 0.14+/-0.04.