A new postoperative rehabilitation program consisting of intensive back training without low back pain being the limiting factor has been tested in a clinical trial and found effective compared to a more traditional training program. The objective of the present investigation was to evaluate the social economic consequences (cost-effectiveness analysis) of the introduction of this new program as a general offer for all patients undergoing first time discectomy for a herniated lumbar intervertebral disc in Denmark. Ninety-six consecutive patients operated on at the Dept. of Neurosurgery. Copenhagen County Hospital of Glostrup were randomized into two intervention groups. One group was offered intensive back training and the other group was offered traditional back training. A historical control group was also selected. The effectiveness of the training programmes was evaluated by a "Low Back Pain Rating Scale" and by the number of patients out of employment one year after operation. The social economic evaluation showed that the new intensive training programme was more effective. Savings in medical expenditure are to be expected if the new programme is offered. Further, as more people are to be expected to keep their employment, a production gain for the society can be expected as well as reduced public expenditures on social benefits.