Background The Dynamic Interspinous Assisted Motion (DIAM) system was designed to stabilize degenerative spinal segments without fusion surgery, maintain segment motion and prevent adjacent segment degeneration. The aim of thisstudy was to investigate clinical efficacy of the DIAM system in treatment of degenerative lumbar disease in China.Methods Eight cases of lumbar vertebral instability were treated with the DIAM system at Peking Union MedicalCollege Hospital from June 2006 to January 2008. There were 6 female and 2 male subjects with a mean age of 46.9years and a range of 40-52 years. Radiographs and scores on outcome measures included the visual analogue scale (VAS) for pain and the Oswestry disability index (ODI). These scores were recorded before surgery and after surgery at intervals of 3-month, 6-month, 1-year and the final follow-up visit.Results The follow-up time ranged from 12-31 months, with an average of 20.6 months. There were significant differences between preoperative and postoperative scores at each follow-up evaluation (P ＜0.05). However, there was no significant difference between each postoperative follow-up score (P ＞0.05). There were significant differences between preoperative and postoperative L4-5 segment activity at each time interval (P ＜0.05), but no obvious difference was found within each postoperative follow-up evaluation (P ＞0.05). The ODI and VAS score improvements were directly correlated with segment activity (r ＞0.7, P ＜0.05).Conclusions The DIAM system appears to be a useful and effective treatment in the surgical management of degenerative lumbar disease in certain patients. However, long-term follow-up is needed to evaluate the clinical outcomes of the device.