alpha-1-antitrypsin (Pi) phenotypes of 548 normal Finnish blood donors were determined by isoelectric focusing in polyacrylamide gel. The frequencies obtained (M, 93.3%; FM, 0.4%, GM, 0.2%; MS, 3.5%; MZ, 2.7%) differed from those reported earlier for a more restricted Finnish population but agreed better with the frequencies reported for other Scandinavian populations. The disagreement with the earlier report was attributed to differences in sampling and laboratory techniques. The present study confirms an earlier finding of a sarcity of fast Pi variants in the Finnish population. One M variant was found. The isoelectric focusing technique used in this study has several advantages over the methods previously described for Pi typing.