The aim of the study was to evaluate of the results of neurolysis in perinatal brachial plexus lesions treatment.Material and methods. Clinical material comprised 31 children, both sex, in age between 3 and 29 months, who had neurolysis of brachial plexus in period from 1998 to 2005. Treatment results have been evaluated in group of 26 children by commonly accepted scales. The shortest postoperative observation period lasted 4 years.Results. Good and very good function of shoulder after surgical treatment has been noted in 14 cases, good function of elbow has been noted in 21 cases. Advantageous position of forearm has been observed in 19 cases. Useful function of wrist in group of upper-middle and total lesions has been found in 18 examined children. Useful motor and sensory hand function has been observed in 7 from 11 examined children with total lesions.Conclusions. Significant compression of brachial plexus neural elements is an indication for their release (neurolysis) also in lesions which have been classified as a I and II degree in Sunderland's scale. In brachial plexus lesions with preserved macroscopic continuity of neural elements (after exclusion of avulsion lesions), intrafascicular fibrosis may be one of reasons of poor neural function improvement.