In order to examine to what extent a gene dysregulation such as Down's syndrome (DS) causes the advance of global biological aging as well as segmental progeroid syndrome, 8 years of longitudinal data were gathered on 14 hematology and blood chemistry characteristics of five adult men and six adult women with DS and four adult men with cerebral palsy (CP). Biological age (BA) was established through the application of principal component analysis based on the data for the same 14 variables of 436 healthy adult men. The BAs of five adult men and six adult women with DS, and four adult men with CP were estimated by using the equation calculated from healthy adult men data, and the BAs were compared. The result of this study indicated that: (1) a genetic condition such as Down's syndrome causes not only segmental progeroid syndrome but also premature aging accompanying global senescence in various organ levels; (2) premature aging exhibited by adult men and women with DS justifies the evidence of primary aging; and (3) the rate of aging for BA in DS patients is nearly a twofold increase as compared to healthy subjects. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.