The present study was undertaken to look at the effect of professional oral prophylaxis on the general health perceptions and lifestyle in workers at a worksite in Aichi-ken. Dental check-ups and three kinds of questionnaires (SAS: The Social Adjustment Scale, MOS: The Medical Outcomes Study and the nutrition) were used in this investigation for three years from 1998. By means of the stratified sampling method, the participants were 265 workers separated into a case and a control group, who work for a pharmaceutical company (201 males, 64 females, average age 35.6 +/- 0.7 yr old). All participants gave their consent to the study. As in the case group, dental hygienists scaled their teeth and gave each of them appropriate advice about their oral health twice in a year. MOS, SAS, nutrition and oral health in the case and control groups were compared with the baseline, third and the final year. The results were as follows; 1) There was significant difference in energy, protein, fat, fish and meats sufficiency rates (p < 0.05) and a higher tendency towards consuming sugar, potassium (K), calcium (Ca), iron (Fe) and Fiber (p < 0.10) in the control group, but there were no significant differences in the other nutrients in the case and control groups. 2) There were significant differences in the number of decayed teeth in the case group, and in the number of filled teeth and decayed teeth in the control group. The gingival condition (CPI = 0) in the case group tended to be higher healthier than the control group, 3) In the MOS questionnaire, the case group was better or not worse in health perceptions scales, pain scales and mental health scales than the control group. 4) In the SAS questionnaire, the case group was better or not worse in the work and the social scales than the control group. It was concluded that oral health, social health and consciousness of health tended to improve by dental intervention.