We observed the clustered star forming complex NGC 1333 with the BIMA and FCRAO telescopes in the transitions HCO+(1-0) and N_2_H+(1-0) over an area with resolution ~10" (0.015pc). The N_2_H+ emission follows very closely the submillimeter dust continuum emission, while HCO+ emission appears more spatially extended and also traces outflows. We have identified 93 N_2_H+ cores using the CLUMPFIND algorithm, and we derive N_2_H+ core masses between 0.05 and 2.5M_{sun}_ , with uncertainties of a factor of a few, dominated by the adopted N_2_H+ abundance.