Spinal instability secondary to metastatic cancer. Fifty-five patients with severe pain from spinal instability secondary to metastatic cancer were referred to Hope Hospital, none being judged to be in a terminal condition. One patient had too extensive disease for surgery so 54 were treated by 55 spinal stabilisations; 49 obtained complete relief of pain and two had partial relief. There were three failures. Twenty-eight of the patients had clinical evidence of spinal cord or cauda equina compression and were decompressed at the time of stabilisation. Of these, 20 had major recovery of neurological function. Patients with pre-operative evidence of extradural tumour had 'prophylactic' decompression at the time of stabilisation; none of these patients later developed signs of cord or cauda equina compression. The results suggest that alleviation of pain and restoration of mobility are best achieved by segmental spinal stabilisation; a few patients require a combined anterior and posterior stabilisation. Postoperative radiotherapy should be given whenever possible, and the causative tumour should be treated by endocrine or chemotherapy, as indicated. 