Polyacrylamide gel electrophoresis of whole histones of calf thymus, chicken erythrocytes, and Tetrahymena was carried out in the absence or presence of a nonionic surfactant, Triton X-100 (up to 6 mM), in 0.9 M acetic acid and 6.25 M urea-0.9 M acetic acid. Calf thymus whole histone was also chromatographed on Bio-Gel P-200 in the absence or presence of 6 mM Triton in 0.01 M HCl and 8 M urea-0.9 M acetic acid. Triton reduced the electrophoretic mobility and distribution coefficient of various histone species in the following order of decreasing effect; H2A greater than H3, H4 greater than H2B greater than H1 in the absence of urea. H1 and specific histones for chicken erythrocytes and Tetrahymena were almost unaffected. Urea antagonized the surfactant effect more for H4 and H2B, and less for H2A and H3. Such surfactant effects can be correlated with the helical contents of histone species under the experimental conditions used, rather than their total hydrophobicites, suggesting that Triton binds to helical regions.