19 samples (1189 individuals) of the commercially fished Patagonian squid Loligo gahi d'Orbigny were collected from Falkland waters between March 1987 and April 1988 and subjected to starch gel electrophoresis. 41 enzyme-coding loci were screened for polymorphism. Clearly resolved enzyme phenotypes were obtained at 21 loci of which six exhibited polymorphism (glutamate oxaloacetate transaminase, GOT-II, E.C. 126.96.36.199.; α-glycerophosphate dehydrogenase, α-GPDH, E.G. 188.8.131.52; isocitrate dehydrogenase, ICD, E.C. 184.108.40.206; malate dehydrogenase, MDH-II, E.G. 220.127.116.11; phosphogluconate dehydrogenase, PGD, E.C. 18.104.22.168; and phosphoglucose mutase, PGM, E.G. 22.214.171.124). Routine scoring at the 21 loci revealed moderate levels of genetic variability, with the proportion of polymorphic loci, P = 0.273, mean heterozygosities per locus = 0.0693, and the effective number of alleles, Ne, with values of 1.13–1.83.