The UV-absorbance of the lysed human leukocyte ultrafiltrate (LLU) was investigated by Sephadex G-15 gel permeation chromatography before and after affinity chromatography on immobilized m-aminophenyl boronic acid. This biospecific fractionation caused substantial changes in 260/280-nm absorbance ratio of individual peaks as revealed by Sephadex G-15 gel permeation chromatography. While the material which had passed through the affinity support unretarded (W) appeared to be partly or completely deprived of peak IV, peaks IV and V were fairly enriched in the retarded material (R). This material, on the other hand, nearly completely missed peaks III, VI and VII. Peak III was copiously represented in material W. Boronate affinity chromatography caused enrichment in the protein content as well as in the content of purine/pyrimidine-bound ribose of material R, i.e. cis-diol group containing (RNA-like) material, considered to represent functional transfer factor activity. The described findings further support the use of immobilized derivatives of boronic acid in the separation of coplanar cis-diol group containing compounds from other constituents of LLU.