Numerous materials have been used to prevent epidural scar tissue after lumbar disc surgery. Free fat grafts are common both experimentally and clinically, but there is some doubt about their protection against fibrosis, and some complications have been reported. In this prospective study, the usefulness of free fat grafts during lumbar disc surgery was evaluated. Ninety-nine patients who had undergone operation due to lumbar disc herniation were divided in two groups: those with implantation of free fat grafts (group A) and those without (group B). Outcome was evaluated at a mean of 2.6 years postoperatively according to the following criteria: visual analog scale for back and leg pain, Hannover Questionnaire on activities of daily living, reflex findings, sensory and motor deficits, consumption of analgesics, walking distance, straight leg raising test, and clinical examination. The outcome variables showed no significant differences between the two groups (P>0.05). This study suggests that the use of free fat grafts during lumbar disc surgery was clinically ineffective.