Since March 1980 to Jan, 1984, 111 cases of L5 and S1 radiculopathies who were diagnosed by electromyography at Dept. of Rehabilitation Medicine, Seoul National University Hospital, was analaysed in retrospective study.

Our aim in this study was the usefulness of tibialis posterior muscle in radiculopathies.

Our results obtationed were as follows.

1) Among the 111 cases, 65 cases (58.6%) were electromyographically positive findings in both anterior and posterior rami, 46 cases(41.4%) were positive findings in only anterior rami.

2) L5 radiculopathies were markedly predominant than S1 radiculopathies in spite of pure or mixed pattern.

3) In L5 radiculopathies, tibialis posterior muscle was the most sensitive muscle in electromyographic findings and in S1 radiculopathies, abductor hallucis muscle was the most sensitive one.

4) The tibialis posterior muscle was more sensitive in pure L5 radiculopathies compared to pure S1 radiculopathies.