A study was carried out of the solution particle size and the iron core size of an iron dextran complex used as a hematinic. The solution sizes were determined by quasi-elastic laser light scattering, and the core size were determined from the line widths obtained from X-ray powder diffraction patterns. The results show that the range of particle sizes in solution (i.e., the diameter of the particle including the iron core and the dextran coat) was approximately 10-40 mm. The iron core (excluding the dextran outer coat) was determined to be approximately similar to 5-6 (+/- 1) nm.