The present Atlas contains adetailed study, based in scanning electron microscopy (SEM) observations, of livingcoccolithophores from NW Mediterranean waters. The study contains 103 figureswith 411 micrographs, which correspond to 168 coccolithophores (includingdifferent taxonomic and morphotypic entities). The figured specimens werecollected during different cruises carried out from 1995 to 1999.Classification of the organisms follows modern taxonomy of living calcareousnannoplankton. Measures of the specimens and notes on their taxonomy are givenin addition to abridged descriptions of the studied taxa. The atlas contains alarge number of previously undescribed forms, specially in the genera Syracosphaera, Papposphaera, Polycrater, Anthosphaera, Corisphaera and Sphaerocalyptra. Several species never illustrated in the literature are presented here forthe first time. Coccospheres having coccoliths of different recognized species arepresented. These combination coccospheres are nowadays considered astransitional steps between different phases in the cellular life-cycle. Anintroduction with a brief overview of the actual coccolithophore knowledge andan abridged glossary with figures of the basic terminology are included.