Stromal-derived factor 1-alpha (SDF-1alpha, or CXCL12alpha) is a major chemokine that controls adult stem cell trafficking. Little is known about its stability after blood sampling, but this is a crucial issue for clinical studies of this molecule. In a study of six subjects, we found total human plasma SDF-1alpha concentrations to be stable for 120 min when the blood is placed on ice immediately after sampling.