Blood losses and transfusions have been analyzed prospectively for 63 lumbar fusion operations in 55 patients. The mean intraoperative loss was 550 ml, with a further 336 ml in postoperative drains. Factors increasing intraoperative loss included posterior vs. anterior approach, the use of instrumentation, multiple levels fused, male vs. female, and younger age. For anterior procedures (without instrumentation and using homograft bone) and single-level posterolateral fusions (PLF) without instrumentation, neither predeposit nor intraoperative salvage (cell saver) was required. Single-level PLF with instrumentation and two-level PLF without instrumentation required either cell saver or predeposit of one or two units. Multiple-level PLF with instrumentation and all 360 degrees procedures required cell saver and two units of predeposit. Two patients received homologous blood.