Nonindigenous species (NIS) are those that have been intentionally or unintentionally introduced outside of their native range as a consequence of human activity. If these species then threaten indigenous species and biodiversity, and/or cause economic damage, they are referred to as "invasive." Biological invasions are not only one of the greatest threats to indigenous marine biodiversity, but they can also cause massive economic and ecological damage. Their presence could also lead to a water body failing to achieve good environmental status under the forth- coming EU Marine Strategy Framework Directive. As the rate of invasion to Great Britain and European waters continues to increase, particularly in light of climate change, the emphasis by member states is on prevention rather than on control or eradication an NIS once an invasive NIS has become established. This paper reviews NIS biosecurity planning for the marine environ- ment, including the most current legislative background, pathway identification and highlights the main issues with the current risk assessment processes. The potential impacts of marine NIS, practical biosecurity measures from Great Britain and internationally are also reviewed. The aim of this paper is to draw attention to the challenges associated with preventing the introduction of marine NIS and to highlight the urgent need for concerted action across the EU member states