The metabolism of xenobiotics is a critical aspect of drug discovery; nowadays, aldehyde oxidase (AOX) has emerged as a key metabolic enzyme having a pivotal role in the failures of several clinical candidates. The lack of homogenous data on possible substrates and not substrates of this enzyme represents a serious limit for the development of an in silico model for metabolism prediction. Here, we present a database of 270 chemically diverse compounds containing aza-aromatic and/or amide moieties (susceptible to human AOX), experimentally tested in vitro. The results herein reported should be useful in the development of a reliable prediction model, which should be of wide interest in chemistry, biology, biotechnology, and medicine.