Exploitation of the commercially-important species of Gelidium in Spain (G. sesquipedale and G. latifolium) and development of the industry occurred after World War II, as a consequence of their use as resources for the extraction of agar. This resulted in the implementation of several harvesting methods, the most important of which is the gathering of cast seaweeds, both from the shore and the sea. From the very beginning, direct exploitation of these species (i.e. plucking) was controversial because of possible adverse ecological effects. Consequently, several biological and ecological studies of both species of Gelidium were begun. This included such aspects as growth, biomass production, productivity, reproduction, regeneration capacity and agar yield. Recently, the growing interest in using and conserving this resource has led to increased knowledge of the biology and ecology of these species. In this paper, we provide an overview of the research carried out by different Spanish groups and suggest guidelines for rational management of these resources.