A study group of 71 non-hypertensive, type II diabetic patients and a control group of 71 hypertensive, non-diabetic patients were recruited for this study, which was performed in a primary health care centre in Al Ain, United Arab Emirates. The aim was to determine the prevalence, nature and relevant associations of psychiatric morbidity among a sample of type II diabetic patients, as compared with a control group of patients with another chronic medical illness (hypertension). A preliminary interview for recording medical history and sociodemographic data was done by primary health care physicians, who also conducted a simple clinical examination for the diabetic group. This was followed by a psychiatric interview by a psychiatrist using the Clinical Interview Schedule. Psychiatric diagnoses for identified cases were recorded according to the International Classification of Diseases-10 criteria, and their severity was evaluated on a clinical basis. There was no significant difference between the prevalence of psychiatric morbidity in the diabetic group (33.8%) and that in the hypertensive group (31%), and both proportions were not significantly more than the proportion previously estimated among primary health care patients in general, in the same centre and using similar methodology. This is against the notion that psychiatric morbidity is particularly more prevalent among diabetic patients than among those with other chronic medical illnesses. The psychiatric morbidity in both groups consisted mainly of generalized anxiety disorder, depressive episode and mixed anxiety and depressive disorders, all of which were of mild-to-moderate severity. However, a high proportion of the diabetic group were distressed by various psychiatric symptoms, not amounting to formal psychiatric diagnoses. Out of the symptoms identified, somatic symptoms, sleep disturbances and irritability were significantly more prevalent than others. The psychiatric morbidity was almost equally distributed between men and women. There was no significant association between psychiatric morbidity and diabetic peripheral vascular disease or peripheral neuropathy.