We have examined the impact on biological systems of some newly synthesised polyoxyethylene polymers using in vitro assays. Toxicity was tested by the 3-[4,5-dimethylthiazole-2-yl]-2,5 diphenyltetrazolium bromide (MTT) assay, haemolysis was assessed, and an ethidium bromide (EB) assay was used to study interactions between the polymers and DNA. All the assay data showed that the polymers are biocompatible. No differences were found between generations (i.e. macromolecule sizes). The results encourage continuing studies on the clinical use of these molecules as drug carriers.