Hydroxytyrosol (HT) is an olive-derived phenol endowed with several biological activities, some of which demonstrated in humans. Indeed, the European Food Safety Authority (EFSA) allows the health claim that HT (≥5mg/d) "protects LDL particles from oxidative damage". In terms of safety, HT has been investigated as the predominant part of raw olive mill waste water extracts that have been granted the Generally Recognized as Safe (GRAS) status. Also, a long-term toxicological study of HT proposed a NOAEL of 500mg/kg/d. As several HT-containing supplements and functional foods are entering the market, we sought to investigate the genotoxic and mutagenic potential of HT, using well-established in vitro models, i.e. the chromosomal aberration assay and the Ames test (by using the Salmonella typhimurium TA 100, TA98, TA1535, and TA1537 strains and Escherichia coli WP2(pKM101)), with and without S9-induced metabolic activation). Even though we cannot rule out that prolonged exposure to HT and its metabolites might have untoward effects, the results of this study indicate that HT is non-genotoxic and non-mutagenic at concentrations that far exceed those attainable after intake.