Members of the gastropod family Littorinidae are common throughout the world. They form a very abundant component of many intertidal and shallow subtidal ecosystems and, by their grazing, often play a central role in shaping these communities. They also display a wide range of life history strategies and many are polymorphic, making them attractive model organisms for ecologists, evolutionary biologists and physiologists alike. Areas of particular interest include ecological interactions with other animals and with algae, the effects of pollutants and the use of littorinids as sentinel species for monitoring pollution, the effects of parasites on growth and ecology, taxonomy, and the study of genotypic/phenotypic responses to environmental factors. There is still much to be done, and the Littorinids are proving to be an ideal group on which to work. The text is primarily targeted at the research level, but should also provide useful information for advanced first-degree students conducting research projects.