Destruction of peripheral nerves with chemical substances such as phenol and alcohol solutions was introduced as a novel therapeutic modality in the 1930s, but it became a popular method of treating severe, intractable pain associated with cancer in the mid 1950s. Severe chronic muscle spasticity often causes constant gnawing pain. Diagnostic nerve blocks with local anaesthetics are sometimes necessary to assess the risk/benefit ratio of chemical neurolysis. Phenol and ethyl alcohol are the drugs most commonly used for peripheral nerve and intrathecal blocks. Chemical neurolysis is most frequently used for blocks of the medial popliteal, the obturator, the sciatic and the musculocutaneous nerve of the arm. A number of factors contribute to the motor functional disability associated with long-standing upper motor neurone lesions. Administration of phenol or alcohol into the intrathecal subarachnoid space is generally reserved for severe symptomatic cases of lower limb spasticity refractory to other methods of treatment.