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In an experimental flock of fowls infectious bronchitis produced reductions in the weights of the whole egg, albumen and shell and a decrease in the ratio of thick + inner thin albumen to outer thin albumen giving the whole albumen a watery appearance. In the thick fraction there was an increase in the water content and a decrease in the concentration of proteins including ovomucin and lysozyme which are believed to combine by electrostatic attraction to form the structural matrix. A reduction in ovomucin concentration was also detected in the outer thin fraction. The deficiency of this protein in the whole albumen was particularly marked and was probably mainly responsible for its abnormal appearance. A reduction in the percentage of ovalbumin I in the albumen proteins occurred in both the thick and the outer thin fractions and in the latter was accompanied by an increase in ovalbumin II. The only other significant changes found in this fraction were increases in the concentrations of sodium and potassium. The estimation of diffusible hexoses and hexosamines provided no evidence that hydrolysis of glycoproteins had occurred. From these and histological findings it was concluded that infectious bronchitis impairs the synthesis of albumen proteins by the magnum.