In this review we list from literature investigations on rat serum proteins using electrophoretic techniques in connection with drug testing. From our own research work, we provide annotated two-dimensional maps of rat serum proteins under control and experimental conditions. Emphasis is on species-specific components and on the effects of acute and chronic inflammation. We discuss our project of structural proteomics on rat serum as a minimally invasive approach to pharmacological investigation, and we outline a typical experimental plan for drug testing according to the above guidelines. We then report in detail on the results of our trials of anti-inflammatory drugs on adjuvant arthritis, an animal model of disease resembling in many aspects human rheumatoid arthritis. We demonstrate a correlation between biochemical parameters and therapeutic findings and outline the advantages of the chosen methodological approach, which proved also sensitive in revealing "side effects" of the test drugs. In an appendix we describe our experimental protocol when performing two-dimensional electrophoresis of rat serum.