This paper presents a review of prehistoric shell midden sites (‘Køkkenmøddinger’) in Denmark. The form and structure of these sites, their contents, distributions, cultural associations, and chronology are discussed. It is concluded that they are not a unique type of coastal settlement but represent coastal, homebase settlements characterised by a dominance of shellfish in the cultural deposits. This is the only aspect by which they differ from the rest of the coastal habitation system. Shell midden sites seem to flourish in periods characterised by a rich marine biotope and coastal habitation can be seen as a direct reflection of variations/changes in the marine biotope.