Layer-by-layer (LbL) assemblies between poly(vinylamine hydtochloride-co-N-vinylformamide) [poly(VAm-co-NVF)] with various amounts of VAm and poly(sodium styrenesulfonate) (PSS) from their aqueous solutions were analyzed by the quartz crystal microbalance (QCM) technique, attenuated total reflection (ATR) spectra, and atomic force microscopic (AFM) observations. QCM analyses revealed that the assembly amount was strongly affected by the VArn content. At a VAm content of less than 30% in total units of poly(VAm-co-NVF), the LbL assembly did not proceed, and the frequency shift zigzagged with the step number. The total frequency shift, however, increased with an increasing step number and with an increasing VArn content. At 30% VAm, the frequency shifted exponentially with an increasing number of assembly steps, and the shift achieved a maximum value, indicating that the greatest amount was assembled with this VAm content. The total shift decreased with a VAm content of 50%. Above 50%, however, the frequency increased linearly with an increasing number of steps, and the total shift after a 40-step assembly was almost the same as that observed with 50% VAm. An assembly mechanism dependent on the VAm content was proposed to explain these observations. AFM observations revealed that the surfaces of the assemblies were smooth at the nanometer level. The VArn content significantly affected the density of the assembly. The density of the assemblies was similar in air and ranged from 1.22 to 1.28 g cm(-3), even though the VArn content differed. On the other hand, the density of the film prepared by using poly(VAm-co-NVF) with a VAm content of 30% decreased to 0.86 g cm(-3) in water, while the density of the film prepared using poly(VAm) was not changed.