We have previously described a statistical model capable of distinguishing young (age<65yrs) from old (age≥75yrs) individuals. Here we studied the performance of a modified model in three populations and determined whether individuals predicted to be biologically younger than their chronological age had biochemical and functional measures consistent with a younger biological age. Those with 'younger' gene expression patterns demonstrated higher muscle strength and serum albumin, and lower interleukin-6 and blood urea concentrations relative to 'biologically older' individuals (odds ratios 1.05, 1.13, 0.61, 0.98; p=3.2x10(-2) , 2.7x10(-4) , 1.1x10(-2) , 2.6x10(-2) respectively). We conclude that our expression signature of age is robust across three populations and may have utility for estimation of biological age. © 2013 The Authors Aging Cell © 2013 Blackwell Publishing Ltd/Anatomical Society of Great Britain and Ireland.