Thermosensitive polymers poly(N-isopropylacrylamide) (PNIPAM), poly(N-vinylcaprolactam) (PVCL) and PVCL grafted with amphiphilic poly(ethylene oxide) (PEO) chains (PVCL-graft-C11EO42) were prepared and characterized and their putative cytotoxicity was evaluated. The cytotoxicity of these thermosensitive polymers and their monomers was investigated as a function of polymer concentration, incubation time and incubation temperature by using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) cytotoxicity tests in Caco-2 and Calu-3 cell cultures. Also, the influence of the chain end functionality on toxicity was examined. Viability (MTT) and cellular damage (LDH) of the cells were shown to be dependent on the surface properties of the polymers, hydrophilicity or hydrophobicity. Hydrophilic PVCL and PVCL-graft-C11EO42 were well tolerated at all polymer concentrations (0.1-10.0 mg/ml) after 3 h of incubation at room temperature and at physiological temperature (37 degrees C). The more hydrophobic PNIPAM induced more clear cellular cytotoxicity at 37 degrees C. The monomers N-isopropylacrylamide and vinylcaprolactam and PEO-macromonomer showed dramatically higher cytotoxicity values with respect to the corresponding polymers. Cell damage was directly dependent on concentration, temperature and incubation time.