The aim of the study was to determine the longitudinal effect of an oral hygiene program on oral levels of volatile sulfur compounds (VSC). The study subjects were randomly selected from patients attending a student course in operative dentistry and from staff members of our dental clinic. The test group (n = 30) received an oral hygiene training including professional toothcleaning (PTC), oral hygiene instruction, and motivation. The control group (n = 10) received no particular treatment. None of the subjects suffered from bad breath nor performed regular tongue cleaning. At baseline, immediately after PTC, one week, and four weeks thereafter we measured the oral hygiene status by means of the papillary bleeding index (PBI) and the oral concentrations of VSC by using a portable sulfide monitor (Halimeter"). Immediately after PTC, as well as one week, and four weeks after entering the program the PBI and the VSC-levels were significantly decreased as compared to the baseline values and the control group. VSCs were decreased by 34.9% (± 6.3) after PTC, 33.2% (± 7.1) one week, and 27.9% (± 5.8) four weeks thereafter. The present study shows that in a group of patients without bad breath, an oral hygiene training program including professional toothcleaning, motivation and instruction of self-applied oral hygiene procedures is capable of reducing both papillary bleeding and oral levels of VSC Halimeter" readings over the observation period of four weeks. Keywords: oral hygiene, oral volatile sulfur compounds (VSC), sulfide monitor