32 patients with Marfan syndrome, diagnosed with DePaepe's criteria, volunteered for this study. All patients underwent standard anteroposterior radiographs of the lumbar spine. Interpediculate distances (IPD) at each level were compared to those of previously established norms. Criteria were developed to determine the presence of Marfan using "cut-off values" for the IPDs at each lumbar level. The IPDs were significantly larger in the Marfan patients at all lumbar levels. Cut-off values were calculated setting the specificity at 95% at each lumbar level. The cut-off value at L4 yielded the greatest sensitivity. We conclude that the IPDs are widened in patients with Marfan syndrome. The IPD at L4 is a good criterion for Marfan with specificity of 95% and sensitivity of 75%. One must consider using this as a skeletal criterion or a screening tool for Marfan.