SUMMARY Four clinical cases of insulinoma in the dog are described. In each, nervous signs increased in frequency and severity over a period of approximately 4 months. Diagnosis was made on clinical signs, blood glucose concentration, response to glucose therapy and, in the 2 cases in which an radioimmunoassay was performed, blood insulin levels. Differential diagnosis and management regimes for insulinomas are discussed. Neocropsy confirmed the diagnoses in 3 cases, with multiple pancreatic lesions being present in 2, and metastases in all 3.