Human gingival fibroblast primary cultures were obtained from healthy donors of different ages (20/50/65 years). The synthesis of extracellular matrix was analyzed and the relative protein production was compared either in different cultures at the same passage or in the same culture at following passages. In the first passages of the 3 cultures the protein patterns resulted similar in quantity and quality. However, a quantitative modification in protein synthesis was evident in each culture during the aging process induced in vitro, with a progressive decrease in global protein production, parallel to the increase of the number of culture passages.