Aimed to prevent Streptococcus pneumoniae biofilm infections, we studied the adherence of nine pneumococcal strains to polystyrene plates and on epithelial cells and the antiadhesive effect of albumin and xylitol. The adherence was variable among strains, but there was a good correlation between their adherent ability and binding to abiotic material and cells. Strains of serotypes 6B and 23F were the most adherent organisms, whereas serotype 3 strains were the least adherent. Human serum albumin (HSA) enhanced bacterial growth at low concentrations (0.5-2.5%) but inhibited it at 10%. Xylitol inhibited bacterial growth of all strains at concentrations ranging from 5 to 15%. Exposure to 0.5-5% HSA in solubilized form and to 5% HSA precoating of plates diminished adherence to polystyrene >80% for all strains, except for serotype 3 strains. Contrarily, 0.5 and 5% xylitol did not diminish significantly pneumococcal adherence to polystyrene plates or on epithelial cells. Our results suggest that 1) the potential application of HSA coatings on medical devices to inhibit pneumococcal adherence and 2) the possible beneficial effect of xylitol in preventing some pneumococcal infections could be because of its antimicrobial activity rather than to an antiadhesive effect.