To determine the mechanisms that might explain retention and/or loss of plankton during the coastal upwelling season, one needs an understanding of the vertical migration behavior and ontogenetic changes in vertical distribution and data on direction and magnitude of currents at depths where the animals reside. In this paper we compare and contrast the cross-shelf distributions of four copepod species, Calanus marshallae, Pseudocalanus mimus, Acartia longiremis, and Centropages abdomalis, and the euphausiid Euphausia pacifica, from sampling during the Coastal Ocean Advances in Shelf Transport (COAST) program. The COAST study region was off central Oregon (44¿--45¿N), ranged from the nearshore zone out to ~1000 m isobath, and was a trapezoid 120 km in length and 40 km wide in the north by 100 km wide in the south. Plankton were sampled along three transects, in the north, middle, and southern portions of the study region. For the two most abundant copepods, C. marshallae and P. mimus, sampling with a Multiple Opening/Closing Net and Environmental Sampling System showed that naupliar and early copepodite stages were found within the warm phytoplankton-rich upper 20 m of the water column but that copepodite stages C3 through adult were found at progressively deeper strata in the water column. Similarly, euphausiid larvae were most abundant within the upper 20 m, whereas juveniles and adults lived deeper in the water column. Diel vertical migration was observed only in the older developmental stages. Because older stages occupy different strata than younger stages, there is cross-shelf displacement of zooplankton.