Best practices for purifying and characterizing G5 poly(amidoamine) (PAMAM) dendrimer are described and current understanding of the material composition and batch variations for commercially sourced material are discussed. Studies have found that by removing many of the trailing generation defect structures, membrane dialysis improves the uniformity of the material. A comparison of panels reveal that the dialysis process reduced the amount of smaller sized dendrimer particles that elute at 22.5 min. The mean number of end groups for the purified Aliquot 1 grade dendrimer was found to be 109 ∓ 5, which is an increase in the mean number of end groups per dendrimer from the unpurified Lot A dendrimer (96 ∓ 5). Clear differences can be seen in the relative amount of the defect structures in each lot.