Polyamine [especially poly(ethylenimine) and poly(4-vinylpyridine)] adsorption onto silica gels for chromatography and water-decontamination experiments, using a Raman microprobe, is reviewed. First, the bare silica are characterized. Then, the polyamines and the adsorbed polyamines spectra are compared. We show that polyamine adsorption onto silica occurs with two kinds of polymer populations : chemisorbed (trains due to important interactions between silanol and the nitrogen atom) and physisorbed (multilayers) polymer. The modifications of chemisorbed polymer bands are stronger than are the physisorbed ones.