Accumulation of plastic in the oceans is recognised as one of today’s major pollution problems and has attracted extensive world-wide media attention. Over the last decade, a significant proportion of the research effort devoted to the impact of the presence of plastics in the environment has focused on studying small plastic particles – so-called microplastics – mostly plastic pellets, fibres and fragments formed by macro-plastic degradation. Research has mainly dealt with the presence of microplastics in surface waters, their role as carriers of micropollutants, either sorbed or originally present as additives in the plastics themselves, and their potential noxiousness to biota. Studies covering all these aspects are included in this Research Front, preceded by two methodology-orientated articles. They will hopefully make a significant contribution to progress in the field rather than merely adding to the many purely descriptive studies currently being published.