The genetic structure of the human population in a random sample of 238 unrelated individuals from Garfagnana (Tuscany, Italy) was studied for five highly polymorphic serum proteins (GC, TF, PI, AHSG, ORM1) and three red cell isozymes (ACP, PGM1, ESD) by isoelectric focusing. Comparison with the gene frequencies from other districts of Tuscany has shown no significant deviation in seven out of eight polymorphic protein systems. Subtype allele frequencies of orosomucoid 1 (ORM1), which were not yet determined in Italian populations, are as follow: ORM1*F1 = 0.586, ORM1*F2 = 0.021, and ORMl*S = 0.393. The most striking features of this unique sample were the relatively high frequencies of PGM1*2B (0.093) and PI*I (0.013) alleles.