Engineered nanomaterials, particularly carbon nanotubes (CNTs), hold great promise for a variety of industrial, consumer, and biomedical applications, due to their outstanding and novel properties. Over the last two decades many different types of CNTs have been produced at the industrial scale. Therefore, the exposure risk to humans associated with such a mass scale production has also increased substantially. This has led to increased concerns about the potential adverse health effects that may be associated with human exposure to CNTs, predominantly because of to their size, their shape, and chemistry. CNTs are also intended for use in many biomedical applications, and therefore their biocompatibility, biodistribution, and fate needs to be carefully assessed. This Minireview intends to highlight the current state of the assessment of potential adverse human health effects possibly associated with CNT exposure, as well as the challenges related to and posed by CNT safety research. The importance of reliability and comparison within and between different studies, as regards the test systems employed, is discussed as well as many other essential aspects relative to CNT safety research, for example efficient and comprehensive characterization, are discussed in the view of an improvement in data collection.