Chromium (III)-albumin complexes that have allergenic properties and induce contact dermatitis are aggregated in solution. This is shown by small-angle X-ray scattering of Cr(III)-albumin solutions at 21°C in a Tris-HCl buffer of pH=7.40.At high concentrations of Cr(III), albumin appears to aggregate to an average molecular weight of an octamer, with an average gyration radius of 116 Å. At low concentration of Cr(III), dimers and also some higher polymers form with an average molecular weight of 135,000 and an average radius of gyration of 57 Å.Analysis of the shapes of the Cr(III)-albumin complexes indicate that they are more elongated than albumin, suggesting that, in the presence of Cr(III), the albumin molecules associate sideways with an expansion mainly of the largest axis.