The vertical disthbution of chlorophyll, zooplankton and physical structure were measured using a pumping system and CTD on two cruises in the Gulf of Maine during June and September 1982. The vertical distribution of chlorophyll was closely related to the density structure of the water column. In waters with a pronounced pycnocline subsurface chiorphyll maxima (SCM) were located at or just above the pycnocline. Chlorophyll concentrations were maximal in the surface waters at those stations sampled in June where the pycnocline was not well defined. The relationship between the zooplankton and chlorophyll distribution differed between cruises. In June, the zooplankton, particularly post-naupliar copepods, were associated with the depth of the chlorophyll maxirnum, while in September the post-naupliar copepods were most abundant in the surface waters above the SCM at the stratified stations. During the September cruise we observed that the copepod nauplii were most abundant at the depth of the SCM, and that the larger protozoans (>35 μm) were most abundant at depths of 55–85 m, which were well below the SCM and pycnocline.