Aims: To evaluate the outcome of surgery in patients with lumbar spine degenerative disease or isthmic spon-dylolisthesis. Methods: Lumbar spine fusion with or without decompression was performed in 132 consecutive patients. Altogether 115 patients attended to follow-up an average 3.4 years after operation. The overall result was assessed by the patient and by an independent observer. Moreover, the disability was measured using Oswestry questionnaire and fusion rate was assessed from flexion and extension radiographs. Results: The complications of surgery were: misplacement of screws in 2 patients, paresis of peroneal nerve in 1 patient, superficial wound infection in 4 patients, breakage of fixation device in 1 patient and spinal fluid fistulas in 2 patients. According to patient’s own opinion the result of surgery was excellent, good or fair in 86 percent of the patients and even 89.6% of them benefited from the surgery. The average postoperative Oswestry score was 28. According to radiographs the fusion rate was 93 percent. At the time of operation 40 patients were retaired and 66 (93%) out of the 75 patients who were still at working age returned to work. Conclusion: Lumbar spine fusion is an effective and safe treatment of degenerative lumbar spine disease and isthmic spondylolisthesis. However, the careful selection of patients is an important factor for success.