Two cases of symptomatic arachnoiditis ossificans in middle-aged women, who had excision of ossified dorsal arachnoidal plaques, are reported. The clinicopathological features and surgical management of spinal arachnoiditis ossificans, which is a rare cause of backache and myelopathy, are discussed. The frequent association of severe contiguous arachnoidal fibrosis is considered to be a major factor accounting for the unpredictable effect of resection of stenosing and compressive ossified arachnoid.