Most cases of diabetes, a complex disorder that requires many lifestyle changes, can be controlled if persons adhere to their prescribed regimen. However, compliance is difficult to attain. Differences in explanatory models between client and practitioner have been suggested as one reason for non-compliance in several disorders. In this ethnographic investigation, individual explanatory models were elicited from persons with diabetes and from health professionals working with these patients. Professionals described models of diabetes in general and their model of a particular patient's diabetes. A composite professional model was constructed and compared with each of the patients' models. The models were most congruent regarding treatment. Etiology, pathophysiology, and severity had less congruence, and time and mode of symptom onset were least congruent. The Spearman correlation coefficient showed a positive but non-significant association of explanatory model congruence between professionals and patients with normal glycosylated hemoglobin levels. Patients and professionals seem to emphasize different domains; patients emphasized difficulties in the social domain and the impact of diabetes on their lives while staff saw diabetes primarily as a pathophysiological problem with impact on patients' physical bodies. This study's importance rests on its clear articulation of significant differences between patients' and staffs' models even when they are similar in demographic characteristics.