The phytobenthos of streams has received a renewed interest since the introduction of the European Water Framework Directive (WFD), with all European member states now being required to monitor stream phytobenthos. This review highlights the reasons for using the phytobenthos as a monitoring tool in water bodies and examines the various biomonitoring approaches adopted. The different possible indices and metrics used for determining the ecological status of a stream using the phytobenthos are evaluated in terms of how effective and inclusive they are. The biological, chemical and physical niches that the phytobenthos occupies in streams are also considered, as well as the functional importance of the phytobenthos to the stream ecosystem as the primary energy source. Multiple factors, such as hydrology, nutrients and grazers, influence phytobenthic growth in streams and these are discussed. All these factors have the potential to limit or enhance phytobenthic growth in different situations and are often interlinked, meaning that the influence of each is difficult to tease apart. This review, however, attempts to look at the current knowledge regarding each factor and discuss how it influences phytobenthic growth in the context of other factors, if such multiple interactions have been researched.