108 elderly patients with lumbar spondylolisthesis were randomized to receive either instrumented posterolateral fusion (n=54) or uninstrumented posterolateral fusion (n=54). The primary outcome of interest was the change in Oswestry Disability Index (ODI) scores after 2 years. Secondary outcomes of interest included back and leg pain on a Visual Analog Scale (VAS), EuroQoL-5D (EQ-5D), Short-Form 36 (SF-36) physical and mental component scores, Zurich Claudication Questionnaire (ZCQ) symptoms and function, length of stay, operative time, total blood loss, drainage volume, autograft weight, and the incidence of fusion and reoperation. There were no differences between the two groups in any of the patient-reported outcome measures at all time points. However, operative time was shorter, and blood loss and drainage volume were significantly lower in the uninstrumented fusion group. The incidence of reoperations was significantly lower in the instrumented fusion group with significantly greater autograft weight and higher fusion rates.