Deglycosylation of oral mucins may be a critical initial step leading to their subsequent proteolysis and putrefaction. The present study was undertaken to determine whether activity in saliva of a major glycosidic enzyme (beta-galactosidase) is associated with oral malodor in a group of 64 subjects. Enzyme activity was detected by the use of a chromogenic substrate (X-Gal) impregnated on paper discs. Malodor-related measurements included two odor judges' assessments of whole-mouth and tongue malodor, and volatile sulfide levels measured by a portable sulfide monitor (Interscan Corp.). Beta-galactosidase assay scores were significantly associated with both odor judges' scores for whole-mouth (p < or = 0.002; Spearman) and tongue malodor (p < or = 0.001; Spearman). Beta-galactosidase activity and sulfide monitor measurements both factored significantly into multiple regression equations for odor judge scores, yielding multiple r-values ranging from 0.47 (p = 0.0007) to 0.60 (p < 0.0001). Analysis of the data presented indicates that beta-galactosidase activity in saliva is correlated with oral malodor.