Forty patients with lumbar arachnoiditis, following previous operations, were classified into 4 myelographic types. Most patients with type I images had herniated disc symptoms with unilateral leg pain and limited straight-leg raising. Patients with types II and III myelographic appearances had bilateral leg pain, absent ankle jerks, weakness, cramps and signs of diffuse sensory deficit; some also had neurogenic claudication and urinary sphincter dysfunction. All patients with type IV had dysesthesia. Twenty-three of the 40 patients underwent reoperation and those with types I and II had acceptable results, but poor results occurred in those with types III and IV myelograms.