Serial blood glucose measurements are currently regarded as the 'gold standard' for evaluating glycaemic control of canine diabetic patients. The aim of this study was to investigate a subcutaneous continuous glucose monitoring system based on microdialysis. Analyses were performed by taking interstitial glucose samples from two different anatomical regions (interscapular region [IR], thoracic region [TR]) in six healthy Beagle dogs during induced hypoglycaemia and hyperglycaemia, the feeding period and a period of stable glucose values. For comparison, plasma glucose concentration was measured simultaneously by a hexokinase-based automated chemistry analyser. The mean absolute differences ranged from 11.7 mg/dL (SD 23.5 mg/dL, TR) to 5.3 mg/dL (SD 19.2 mg/ dL, IR) with a correlation of r = 0.43-0.92 (P < 0.01 ). Sensitivity for the detection of hypoglycaemia was 85.0% TR and 93.3% IR, and the specificity was 99.5% TR and 99.7% IR, respectively. In a modified Clarke error grid analysis, 99.3% TR and 99.7% IR of the values fell into zone A and B. Collapse of the microdialysis fibre was a recurrent problem although this was easily detectable by fluctuations in system pressure. The microdialysis system reflects physiological as well as induced variations in blood glucose in a valid manner. [ABSTRACT FROM AUTHOR]