H1-histone (H1) purified from calf thymus was subejcted to nonenzymatic glycation in vitro. A lysine residue in a restricted environment, with an apparent pKa of 6.9, was glycated, notwithstanding the high lysine content of H1. The extent of glycation per lysine residue was 2.4 times larger than that of human serum albumin. Fluorescence at Em. 420 nm (Ex. 340 nm) was closely correlated to the degree of glycation.