Background: Deviations observed during operations triggered our effort to initiate an investigation concerning variations in the formation of brachial plexus. Material and Methods: In 50 cadavers of adult subjects the authors examined 100 brachial plexuses in order to detect incidence of neural variations. The participation of the C4 radix or Th2 radix as well as various variants from outlets of individual radices and their branches from the vertebral column to the variants in the formation of nerve trunks was investigated. The attention was devoted to their course, anastomoses, thickness and occasional absence. In addition to anatomical complexity and variability, attention is paid to motor innervation peculiarities in relation to diagnosis. The attention is paid to the mechanisms and morphological reasons in the origin of certain type of injuries. Results: the prefixed type occurred in 24 cases (48%), the postfixed one in a singe case. In 25 cases (50%) 32 deviations were observed. The deviations were more frequent on the left side in 11 cases. Conclusion: The study made it possible to find out and describe exceptional, so far unpublished, anatomical deviations in the formation of nerve radices and trunks of brachial plexus.

        Key words: brachial plexus – nerve radices – nerve trunks – variations