We have reviewed the clinical and pathological data of a series of 100 consecutive diabetic patients with symptomatic neuropathy in order to learn more about the causes of neuropathy in this population and on the signs and symptoms that could suggest another cause than diabetes in this setting. After diagnostic procedures, patients were assigned one (at most two) of a final total of 18 different causes of neuropathy. Diabetes accounted for 74 % of the neuropathies in the whole group of patients and for 79 % of those with a fiber length dependent pattern of neuropathy. One third of patients had a neuropathy unrelated to diabetes. As a group, 71 % of the patients presented either a length dependent diabetic polyneuropathy (LDDP) or a proximal diabetic neuropathy (PDN). The LDDP group was biased towards more severely affected patients owing to our specialization. Conversely, most patients with proximal diabetic neuropathy had usual features. Chronic inflammatory demyelinating neuropathy that was diagnosed in 9 % of the patients was the most common non-diabetic cause of neuropathy in this population. We conclude that a short interval between diagnosis of diabetes and the onset of the neuropathy, early motor deficit, markedly asymmetrical deficit and generalized areflexia, which are all uncommon in the LDDP, argue in favor of a non diabetic origin of the neuropathy and should lead to further investigation.