Polyurethane (PU)-solid wood composites were prepared by impregnating PU prepolymer into low-density fast-growing poplar solid wood and controlling the prepolymer Cured or foamed within wood voids in the presence of the catalysts triethanolamine (TEA), diethylenetriamine (DETA), triethylenediamine (TEDA), and N-methyl morpholine (NMM), respectively. A scanning electron microscope (SEM) was used to observe the morphologies of the cured PU resin and the wood voids, and the effects of catalyst species on the mechanical properties and dimensional stabilities of PU-wood composites were evaluated. The results indicated that the PU prepolymer Cured in the presence of various catalysts resulted in different morphologies and distributions within wood voids, and therefore led to various mechanical properties and dimensional stabilities of the PU-wood composites. Because of the fact that wood cell walls in the surface layer had apparently collapsed in the presence of catalyst DETA and therefore the wood was densified, the PU-wood composite prepared with DETA had the best mechanical properties and dimensional stabilities. The PU prepolymer was well impregnated and evenly foamed within the wood in the presence of catalyst NMM, giving the PU-wood composite prepared With NMM Much better dimensional stability as the foamed PU blocked the water transfer between the cells. (c) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 12931299, 2009