It has been shown that the recovery of monomeric antibodies from protein A affinity chromatography is enhanced significantly by using arginine as an eluent. To extend the applications of arginine to antibody purification and obtain an insight into the mechanism of arginine elution, we compared arginine with citrate, guanidine hydrochloride (GdnHCl), arginine derivatives, and other amino acids in protein A chromatography. We also applied arginine to elution of polyclonal antibodies (pAbs) in antigen affinity chromatography. As described previously, arginine was effective in eluting monoclonal antibodies IgG1 and IgG4. Two arginine derivatives, acetyl-arginine and agmatine, resulted in efficient elution at pH 4.0 or higher, and this was comparable to arginine. On the other hand, other amino acids, such as glycine, proline, lysine, and histidine, are much less effective than arginine under identical pH conditions. Whereas elution increased with arginine concentration, elution with citrate was insignificant in excess of 1 M at pH 4.3. Arginine was also effective in fractionation of pAbs using antigen-conjugated affinity columns. Although GdnHCl was also effective under similar conditions, the eluted material showed more aggregation than did the protein eluted by arginine.