Samples of resting and stimulated whole saliva and stimulated parotid saliva were collected from 40 young adults. One week later, after 48 h on a standardized diet without oral hygiene, all available plaque was collected for dry weighing. An inverse relationship was found between the 'free' lysozyme concentration in stimulated parotid saliva and plaque dry weight (r = -0.46, p less than 0.01). There were no other statistically significant correlation coefficients between concentrations of individual salivary constituents and plaque dry weight. However, cluster analysis of constituents in resting whole saliva revealed three groups of subjects with different salivary profiles, and in particular with different concentrations of both IgA and hypothiocyanite. Subsequent analysis revealed differences in plaque dry weight between the groups, demonstrating the potential biological significance of cluster membership based on salivary factors.