One hundred and two dentate patients with type II diabetes mellitus and 98 non-diabetic subjects were examined for oral conditions and metabolic state. Self-reported health behaviour was analysed. From factor analysis four factors emerged: general health behaviour (GHB), perceived fatigue (PF), diet control (DC) and regular diet (RD). In diabetics PF, DC and RD were significantly higher than that in non-diabetics. Patients with diabetes were more likely to control their disease through a programme of decreased kilojoule intake leading to weight management. However, they tended to tire. The mean gingivitis index was significantly higher (p<0.01) among diabetics (2.39) than among nondiabetics (1.99). The number of missing teeth was significantly higher (p<0.01) for diabetics (6.7) when compared with non-diabetics (4.3). On the other hand, aetiological factors (plaque, calculus) and the level of dental health behaviour as expressed in the HU-DBI scores were similar. Probing pocket depth did not differ statistically between groups. The increasing number of missing teeth in diabetics may primarily result from severe periodontitis with tooth mobility or deep pockets. Findings in this study suggest that the difference in the severity of periodontitis between diabetics and non-diabetics was significant although aetiological factors and the level of dental health behaviour were similar.