Experiments were conducted on the grafting of end-functionalized free chains from dilute solution to a solid bearing a preexisting polymer brush. The hypothesis was that grafting behavior would parallel the theoretical predictions made for penetration of a preexisting brush by free chains. Paralleling penetration theory, the grafting of free chains increased with concentration of the bulk solution and decreased with molecular weight of the free chains, although the decrease was less pronounced than predicted by theory. Free chains chemically identical to, but longer than, the chains in the brush did not become grafted. However, free chains longer but more flexible than the chains in the preexisting brush did become grafted. Contrary to penetration theory, which predicts an exponential decrease in penetration with grafting density of the preexisting brush, grafting of free chains (of three different molecular weights and two different chemical structures) appeared to have little to no sensitivity to density of the preexisting brush. This insensitivity, unexplained at present, suggests that there are aspects of penetration that have not been identified by theory and also suggests a direction for future experiments. One of the most surprising findings was the rapidity with which free chains penetrated the preexisting brush. They became grafted almost as rapidly as free chains diffuse to a bare surface to form a mushroom layer. This indicates that the preexisting brush does not constitute a strong barrier to diffusion of free chains but, instead, facilitates their diffusion to the surface.