Small and large fibre function was studied in 40 non-ketotic, newly diagnosed Type 1 diabetic patients and 48 age-matched controls, using 12 quantitative tests for assessment of cutaneous sensation. Patients were aged 10-39 years and had been treated with insulin for 4-31 days. Thermal discrimination (foot), warm and cold thermal perception (thenar eminence and foot), and heat and cold pain perception thresholds (thenar eminence) were significantly elevated in the patients as compared with the controls (p less than 0.05 to p less than 0.001). No significant differences in thermal discrimination (thenar), heat and cold pain perception (foot), and metacarpal as well as malleolar vibration perception thresholds were noted between the groups. The rates of abnormalities among the individual tests ranged from 0% to 27.5%, being lowest for vibration perception and highest for thermal perception thresholds after cold stimuli. The results in nine of 12 tests correlated significantly with age, but only two were related to HbA1c. Thus, sensory neural functions transmitted by small fibres, but not those transmitted by large fibres, were impaired in newly diagnosed Type 1 diabetics after the correction of initial ketosis and hyperglycaemia. Cooling perception tests were most sensitive in detecting abnormality. An age-related involvement of different small fibre functions was present in these patients.