Deep chlorophyll a maximum (DCM) was found in the 80-110 m deep northeastern coastal Adriatic (Pag and Velebit Channels) in July 2007. Eight times higher concentrations of chlorophyll were determined in the 50 to 60 m DCM layer (0.81 to 0.91 mu gL super(-1)) relative to the surface waters. According to thermohaline conditions and phytoplankton biomass distribution, over the greater part of the considered area the water column was separated into three layers (the surface layer approximately 10 m deep, the subsurface layer extending between 10 and 50 m, and the deep layer found below 50 m depth) and three distinctive regimes were detected (in the South Velebit Channel, the Middle Velebit Channel, and the Pag Channel). This is the first evidence of the deep chlorophyll maximum in the eastern coastal Adriatic Sea. Deep chlorophyll maxima were composed of picoplanktonic, rounded cells, probably cyanobacteria (1.2 mu m in size, 8 x 10 super(3) - 1 x 10 super(4) cells mL super(-1)).