This paper presents a study of the qualitative and quantitative composition of the phytoplankton from the Alboran Sea during two cruises carried out in January and April 1982. The phytoplankton was dominated by small flagellates and diatoms in both cruises, but chlorophyll a concentration and cell abundances were higher in April. The main geographical feature concerning phytoplankton distribution was the presence of a rich zone in the sector between Algeciras and Adra and two poorer zones in the eastern and western parts of the area studied. The results are discussed in relation to the hydrography of the area.