Aim: The difference in consistence of the nucleus pulposus and the annulus fibrosus allows the water jet to selectively remove the nucleus in a closed vertebral disc at a certain pressure range. The aim of the study was to investigate the use of water jet cutting in microinvasive spinal surgery. Methods: A comparison in terms of efficiency between the water jet and those of the laser and APLD (automatic percutaneous lumbar discotomy) was achieved by plastic reconstruction of the resected spaces using the in-vitro-model of the spinal column of young pigs. The in-vitro-study was followed by a prospective clinical study with 21 patients. Results: The in-vitro-employment of the three different methods showed that there were no significant differences in volume of the removed nucleus material. During the use of the hydro jet at 50 bar and simultaneous suction the intradiscal pressure measured in vitro remained below 1 bar. Clinical tests on the 21 patients showed good to very good results in 71% of the patients tested (mean follow-up 5.8 months). No complications were found. As working mechanism the pure mechanical effect and the influence on chemical processes within the nucleus remain points for discussion. Conclusion: The current studies results demonstrate that hydrojet spinal surgery might be a safe new method for surgery of disc protrusion and contained prolapse.