We evaluated the reliability of serum beta 2-microglobulin (beta 2-MG) in comparison with serum creatinine, blood urea nitrogen and creatinine clearance in 164 patients with spinal cord injury. The value of serum beta 2-MG demonstrated the highest correlation coefficient (r = -0.927) in relation to creatinine clearance. The beta 2-MG value reflected the severity of hydronephrosis on excretory urography, with very few false negative values. The value of beta 2-MG is concluded to be one of the best screening tests in evaluating renal function in spinal cord injury patients.