Poly(vinylamine hydrochloride-co-N-vinylformamide) [poly(VAm-co-NVF)] with variable VAm content, and a weak polyacid poly(acrylic acid) were assembled on a quartz crystal microbalance QCM) substrate from their aqueous solutions, thus forming polyelectrolyte multilayers. The effects of varying the VAm content on assembly profiles and film structures were analyzed by quantitative QCM analysis, attenuated total reflection spectra techniques, and atomic force microscopic observation. At a VAm content of less than 40% of the total number of poly(VAm-co-NVF) units, the layer-by-layer assembly did not proceed, and the frequency shift of the QCM zigzagged with the step number. Above 40% VAm content, the frequency increased continuously with an increasing number of steps. The assembly amount was also maximal at 40% VAm content. The films obtained swelled with water molecules, and this swelling was followed by an increase in thickness in the aqueous phase. The results obtained were compared to those obtained from a combination of poly(VAm-co-NVF) and a strong polyacid, poly(sodium styrenesulfonate). (c) 2006 Wiley Periodicals, Inc.