Lysozyme titers in pure secretions of human parotid and submaxillo-lingual salivary glands were determined by turbidimetric methods. Mean lysozyme values in parotid secretions were equivocal ([image] 21.0 [mu]g egg white equivalents/ml), depending upon methods of gland stimulation. Inter-action of the parotid and submaxillo-sublingual secretions of 30 normal young male adults revealed an inhibition of the parotid enzyme by some component in the submaxillo-sublingual saliva. An isolated mucopoly-saccharide from submaxillo-lingual saliva showed competitive inhibi-tion of the parotid saliva lysozyme. This parotid lysozyme inhibitory factor had no effect upon lysozyme occurring in the submaxillo-lingual secretion (73.4 = S.D. 29.3 [mu]g/ml). Accordingly, increased or ab-normally high total salivary lysozyme titers were concluded to be an expression of the quality or quantity of the submaxillo-lingual saliva mucopolysaccharide and/or the quantity of the parotid saliva lysozyme secreted.