A method is described that can help preventing the mass killing of frogs when only minute samples oftissue-specificallyblood-are needed, such as for electrophoresis ofproteins in aid ofpopulation genetic studies. About 10 microliter of serum were rather easily collected from the feet, while the animals (belonging to several forms of Rana esculenta complex) stayed relatively unharmed. By means ofvertical electrophoresis in I mm thick polyacrylamide gels several protein patterns were demonstrated in samples as small as I microliter of serum (plus 1 microliter sucrose solution). Patterns of albumin, LDH and esterase could easily be analysed and were compared with literature data. Some more experimenting might result in the production ofgood zymograms ofa-GDH and PHI too. AAT, PGM and CK appeared to be absent in serum but could easily be demonstrated in samples from skeletal muscle.