The binding of europium and americium by an aquatic fulvic acid was investigated using an equilibrium ion exchange technique (Schubert's method). The results for europium were consistent with literature data. Americium gave anomalous results for both the Do values (partition coefficient of the metal between the resin and solution phases in the absence of the fulvic acid) and D values (partition coefficient of the metal between the resin and solution phases in the presence of the fulvic acid). The values for americium were unexpectedly low and, in the case of D values, only slightly pH dependent. The cause of the discrepancy was found to be the partial dissolution of the resin or the loss of small colloidal material from the resin. The effects on the europium results were minimal due to the use of lower resin weights and higher metal concentrations.