Poly(vinyl alcohol) (PVA) and poly(methyl methacrylate) (PMMA) were assembled from NaCl-containing aqueous and organic solutions, respectively, by their stepwise physical adsorption onto a quartz crystal microbalance (QCM) substrate, which enabled the quantitative analysis of the assembly process. The layer-by-layer (LbL) assembly was demonstrated by a frequency shift in the QCM, as well as by an analysis of the static contact angles. A reflection absorption spectrum of the LbL assembly revealed the presence of the polymers in the assembly. Atomic force microscopic observation indicated the surface to be molecularly smooth. Chloroform and toluene were suitable solvents for the PMMA assembly. The amount of polymer assembled increased upon increasing the NaCl concentration in the aqueous PVA solutions. The assembling mechanism was proposed based on these analyses. The LbL assembly could be significantly extended to combinations between PVA and, other hydrophobic polymers such as polystyrene, poly(D,L-lactide), and poly(dimethylsiloxane). Not only interactive polymer combinations but also the combinations between PVA and hydrophobic polymers were significantly assembled in an LbL manner.