The Deep Chlorophyll Maximum (DCM) is simulated in two oligotrophic regions (SW Sargasso Sea and NW Mediterranean) using a physical/biological model that couples an upper ocean turbulent model to a nutrient/phytoplankton model. The biological model considers two types of primary producers, heterotrophs and atmospheric in addition to internal nitrate inputs. Model results appear to adequately reproduce the DCM structure in those regions. The DCM depth and magnitude is mainly determined by the vertical eddy diffusion and light extinction. The grazing parameters mainly affect the intensity of the DCM. This suggest the DCM is primarily the result of a balance between upward nutrient flux and light field characteristics. Consequently, the regenerated production only plays a secondary role.