A derivative containing matrix-bound (MB) subunits of aldolase was prepared by attaching native tetrameric aldolase to Sepharose to form MB-aldolase followed by dissociation with 6 M guanidinium chloride and renaturation. The interaction between the MB-subunit aldolase derivative so prepared and subunits added in solution was studied. Nascent subunits of aldolase were generated in situ by diluting a small aliquot of guanidinium chloride-denatured aldolase into a much larger volume of buffer containing a suspension of MB-subunit aldolase. This treatment caused a significant increase in the amount of bound activity. The ability of MB-subunit aldolase to pick up activity from solution is highly specific. After repeated treatments with nascent sub-units, the matrix-bound activity reached a saturation level close to four times the activity of MB-subunit aldolase. The product of this treatment is very similar in properties to the original MB-tetrameric aldolase but different from MB-subunit aldolase. These observations suggest that MB-subunit aldolase can associate with nascent subunits generated in solution to form MB-tetrameric aldolase. The results in this paper support the conclusion from the kinetics of renaturation (Chan et al. J. Biol. Chem. 248, 2778 (1973)) that aldolase monomers have the same activity whether they exist singly or as part of a tetrameric structure.