Two members of a Japanese family (male and female) with serum pseudocholinesterase (ChE) activities elevated two to three times of the normal mean were studied for isozyme pattern by polyacrylamide gel slab and gradient gel slab electrophoresis. Beside the normal ChE bands, additional bands were observed: one between minor C3 and C4 bands, one cathodally to major C5 and one (or two) cathodally to C6 band. All the bands disappeared upon treatments with antibodies to normal ChE and also with ethopropazine. The serum ChE had normal dibucaine and fluoride numbers. In view of the fact that the properties of ChE isozyme in the present cases do not correspond to any of the described one, the variant ChE was named E. Takamatsu after its place of origin.
