The aim of this study was to evaluate an infrared light absorption (ILA) method for registration of dryness of the oral mucosa. Measurements were performed in the buccal and in the lip mucosa immediately before and every 30 min after submucosal injection of 1.0 ml methylscopolamine nitrate in nine healthy subjects. For comparison, a dental mirror sliding friction test was used. About 1.5 h after injection the ILA method showed statistically significant (P less than 0.01) decreases of values in both the buccal and the lip mucosa. However, in the individual subjects the deviations from initial values showed only slight agreement when measured with the ILA method and the mirror friction test. Thus, the ILA method does not seem to be suitable for registration of individual variations in oral mucosal dryness.