The interaction of -chymotrypsin covalently bound to quaternized poly(4-vinylpyridine) with oppositely charged latex particles was investigated and compared with that of free a-chymotrypsin. The free enzyme and the corresponding polymer conjugates were added to a mixture of two latexes: one coated with bovine serum albumin and the other with specific inhibitor of a- chymotrypsin. The polycations themselves were found to be nonselectively adsorbed on oppositely charged latex surfaces. However, the ca-chymotrypsin-polycation conjugates, as well as the free enzyme, were selectively adsorbed on the latex surfaces coated with the enzyme inhibitor. The results are considered to mimic the search and recognition mechanism for target cells by polyelectrolytes carrying a specific vector moiety.