Suspension-feeding bivalve molluscs are foundation species in coastal intertidal systems. The selective feeding capabilities of these animals can have a large influence on phytoplankton communities and nutrient flow to the benthos. Particle selection, including the types of particles chosen for ingestion and the possible mechanisms mediating selection, has been studied extensively and reported in the literature. To date, however, the possible mechanisms mediating these selective processes have remained elusive. Generally, the focus on a few key commercial species, and their demonstrated range of selective capabilities, has made it difficult to design studies that elucidate the mechanisms behind particle selection. This review focuses on key research that has been carried out in the last 20 y toward better understanding the mechanism that underlays selective capture and ingestion of particles in this important group of animals. Recently, work has been completed which has advanced the field in pointing to a passive mechanism as a mediator of selection, with the interactions between the physicochemical properties of particles and the mucus covering the pallial organs most likely mediating food choice. Although no strong evidence for an immediate, active mechanism which underlies particle selection was found, avenues for future research are suggested in this review. The possible mechanisms that control capture, including qualitative precapture selection, are also summarized and discussed in depth. Methodological considerations for rigorous experiments to advance the field are also discussed, including suggestions of general guidelines for experimental designs, which will allow better comparison of findings across studies.