Peroxisome proliferation in rodent liver is a good biochemical marker of toxicology for several classes of xenobiotics, including fibrates; phthalates and adipates; or chlorophenoxy-acetate, a herbicide. Research in peroxisomes provides a good example of the integration of fields related to basic sciences and biomedical and industrial health. A 25min video programme illustrates techniques involved in the characterization of purified peroxisomes (Fig. 1) and membranes, immunoblotting, measurement of proliferation markers, mRNA analysis at the post-transcriptional level, DNA techniques, cell cultures as biological models and computer analysis. It is aimed at undergraduates and non-biochemist advanced students in biology.