Nanofibrillated cellulose (NFC) systems are today on the height of the attention of the research community and the industry, thanks to their perceived potential in a sustainable society scenario. A related field that has seen an upsurge of interest is the rheology of NFC-based systems, as it is in the heart of the processing of these materials both in the manufacturing step and its industrial applications. However, despite considerable efforts the progress in the field has been sluggish. This is partly traced to, among others, the unsatisfactory disclosure of the experimental set-up in the published work (which hinders independent evaluations) and unawareness of the different characteristics of different NFC systems, which require careful set-up of the experiments. In this light, a few of the complicating aspects with regard to rheological studies of NFC-based systems are exemplified, and some of the more important features of the rheology of nanocellulosic systems with emphasis on single-component NFC systems are reviewed. The authors thereby hope to contribute to a better understanding of the already- published results, and inspire future contributors to address the earlier-mentioned inadequacies.