The hemolytic activity and the cytotoxicity of PEG-based solubilizing agents on Caco-2 monolayer were investigated. In vitro tests can predict the irritancy potential and the delayed toxicity of the surfactants. There were significant concentration dependent differences between the result of the MTT (3-(4,5-dimethylthiazol-2-yl))-2,5-diphenyltetrazolium bromide) test and the data of the hemolytic activity test. Our investigations show that safer and more applicable tensides can be selected in order to form a more biocompatible medicament.