In 1964, Vincent Allfrey and colleagues reported the identification of histone acetylation and with deep insight proposed a regulatory role for this protein modification in transcription regulation. Subsequently, histone acetyltransferases (HATs), histone deacetylases (HDACs) and acetyl-Lys-binding proteins were identified as transcription regulators, thereby providing compelling evidence for his daring hypothesis. During the past 15 years, reversible protein acetylation and its modifying enzymes have been implicated in many cellular functions beyond transcription regulation. Here, we review the progress accomplished during the past 50 years and discuss the future of protein acetylation.