Blood group systems ABO, KEL, MN, RH, secretor status for ABH blood group substances, red cell enzymes ACP1, ESD, AK1, 6-PGD, PGM1 subtypes, serum markers GC, TF, PI, AHSG, ORM1 and chromosomal heteromorphism Q, C, DA/DAPI were examined in a population sample of the Garfagnana, a semi-isolated mountainous area in the province of Lucca (Tuscany, Italy). The total sample was subdivided and analysed according to the more recent historical events which have occurred in Garfagnana. The observed phenotype and gene frequencies were discussed in the context of other population samples from the same province and of the same region. As a whole, the results concur in pointing out a certain degree of heterogeneity within the area and a high differentiation from the rest of Tuscany. Such peculiar genetic features of the population have to be related to the historical, geographic and cultural isolation of the Garfagnana.