Esterase zymograms from single homogenates of A. atroparvus larva, obtained by isoelectric focusing in polyacrylamide gels, have shown a higher amount of enzyme fractions (16-18) compared to the usual number of bands (6-7) which can be observed after electrophoresis on polyacrylamide vertical gel slabs at a continous pH value. The significance of the finding and its applicability to problems of formal genetics of enzymes, have been discussed. The conclusion is that, the electrofocusing technique does not seem to facilitate the finding of gene-enzyme systems. It has been suggested that this technique could be successfully applied to well defined analytical problems, for example the analysis of electrophoretic patterns produced by heterozygous variant forms of multimeric enzymes.