In 1987-1988 the authors subjected to comprehensive neurological examination 79 type I diabetics. The group comprised subjects under 60 years and patients with other possible neurotoxic influences were eliminated. After a detailed clinical examination in 75.9% diabetics clinical signs of affection of the peripheral nervous system were revealed, incl. 45.6% clinical diabetic neuropathies were detected. In all instances it was symmetrical distal sensory or sensomotor polyneuropathy and in four instances moreover the carpal tunnel syndrome was detected. The most frequent neurological disorder was panhypaesthesia on the acra of the lower extremities. The most frequent subjective complaint were paraesthesias of the feet and subsequent cramps. The authors investigated moreover parameters of the long-term compensation of diabetes, the duration of diabetes and the biological age of diabetics. They assessed the statistical significance of these parameters for the development of diabetic neuropathy which was proved only for the parameter of the duration of the disease and the biological age of type I diabetics (p less than 0.05).