A range of dextrans (5, 10, and 70 kDa) were covalently bound to smooth silica slides and porous (500 Angstrom) silica particles with an external diameter of 25 mu m. AFM analysis of the slides in air has shown the presence of discrete, clustered, and in a few regions overlayered dextran molecules, which exhibit increasing diameter and decreasing packing densities with increasing molecular weight. Analysis of 10 and 70 kDa dextran bound to silica particles has revealed surface features consistent with those of the dextran molecules, superimposed upon the morphology of the underlying silica particle.