We report the in vitro selection of DNA aptamers that bind to histone H4 proteins acetylated at lysine 16. The best aptamer identified in this selection binds to the target protein with a K-d of 21 nM and discriminates against both the nonacetylated protein and histone H4 proteins acetylated at lysine 8. Comparative binding assays performed with a chip-quality antibody reveal that this aptamer binds to the acetylated histone target with similar affinity to a commercial antibody but shows significantly greater specificity (15-fold versus 2400-fold) for the target molecule. This result demonstrates that aptamers that are both modification and location specific can be generated to bind specific protein post-translational modifications.