It is of great interest to investigate how malocclusion affects oral hygiene, caries, periodontal diseases and so forth. Young adults 19 to 28 years of age, students in a dental school, a school for dental hygienists, a school for dental technicians and so on, were selected as subjects. Conditions of malocclusion were observed by means of OFI (Occlusion Feature Index), Malalignment Index, LI to 1-6 angle, LI to 1-7 angle, and an orthodontic judgement. Conditions of oral hygiene were observed by means of DI (Debris Index), CI (Calculus Index), and OHI (Oral Hygiene Index), conditions of caries by means of DMFT-I (DMFT Index), and DMFS-I (DMFS Index) and conditions of periodontal diseases by means of PMA-I (PMA Index) and PI (Periodontal Index). Stature, body, weight and girth of the chest were of help in the to observation of physical conditions. Mean values and standard variations in all subjects, and separate values for males and females were obtained. In addition, a significant diffrence between males and females was sought by an analysis of variance, and correlations between the various items were reviewed in detail, and relations, between orthodontic judgements by the author and OFI were also examined. In conclusion, significant differences for each item in males and females, and correlations between the various items were shown.