PURPOSE: The purpose of this study was to determine if the program focusing on gluteal muscle exercise combined lumbar stabilization had an effects on pain, functional disability and lumbar instability in chronic low back pain patients who had lumbar instability. METHODS: Thirty four patients were recruited in this study. The participants were randomly allocated stabilization exercise group (SEG) (n=17) and gluteal muscle exercise group (GEG) (n=17). The gluteal muscle exercise group conducted gluteal muscle exercises combined lumbar stabilization and stabilization exercise group did only lumbar stabilization exercise for 30 minutes three times a week for six weeks. Pre-exercise assessment tools, visual analogue scale (VAS) and Korean version Oswestry Disability Index level (KODI) were used for pain and functional disability each. Also, these were scored by the tool of lumbar instability. The pain, functional disability levels, and lumbar instability after six weeks with this exercise were re-evaluated. RESULTS: First, SEG showed a significant decrease in the lumbar pain, functional disability levels and lumbar instability. Second, GEG showed a significant decrease in the lumbar pain, functional disability levels and lumbar instability. The third, GEG showed even more significant decrease in the lumbar pain levels, functional disability levels and lumbar instability than SEG. CONCLUSION: Gluteal muscle exercises combined lumbar stabilization are more effective than only lumbar stabilization exercise in the pain levels, functional disability levels and lumbar instability for the chronic low back pain patients with lumbar instability.