Dispersions of very small metal particles in polymeric matrixes are scientifically and technologically important. Here, poly(N‐vinylpyrrolidone) (PVP) filled with nanometric silver particles characterized by a narrow size distribution and a controlled average dimension has been obtained using a modification of the polyol process. In particular, the nanocomposite material was prepared by reduction of silver nitrate in ethylene glycol in the presence of ultrasound and PVP as a protective agent. The final particle size was controlled by removing the silver–PVP system from the reactive mixture by addition of acetone. The UV–visible spectrum of the material shows a very strong plasmon resonance band centred at 410 nm. The band position depends on the particle size and, consequently, the control of the particle growth process allows one to modulate the nanocomposite absorption wavelength. Such an important characteristic offers the possibility to use Ag–PVP nanocomposites to produce UV‐absorbers and colour filters for advanced optical devices. Copyright © 2001 John Wiley & Sons, Ltd.