Human gingival fibroblast primary cultures were obtained from healthy donors of different ages (20/50/65 years). The identity and homogeneity of the histotype were determined by immunofluorescence of cytoskeletal intermediate filaments (vimentin versus cytokeratin). Cell growth characteristics and doubling times, determined by growth curves, were compared in the same culture, during aging process induced in vitro, and also in cultures from donors of different ages. A progressive decrease of proliferation was found during both physiologic aging in vivo and induced aging in vitro.