Cataractous lenses produced by hydrocortisone or prednisolone treatment in developing chick embryos turned golden brown on heating at 100°C for 60 min. Analysis of an 80% ethanol fraction from the lenses, which contained the pigment-forming substance(s), demonstrated that the heat-induced pigmentation was related to the appearance of opacity of the lens after glucocorticoid administration and suggested that the pigmentation occurred by the Maillard reaction between glucose and amino acids.