Shell calcification rates of four species of euthecosomatous pteropods and two species of shelled heteropods were measured in short-term 45Ca uptake experiments. In subtropical, temperate, and subarctic waters of the North Pacific Ocean and Atlantic Ocean, animals were hand-collected by Scuba divers, captured with the use of a submersible and caught in plankton nets. Shell growth rates of pteropods ranged from 1.1 to 7.8 μg Ca deposited (mg Ca shell)−1 h−1. Heteropod growth rates ranged from 4.6 to 4.9 μg Ca deposited (mg Ca shell)−1 h−1. Aragonite production of shelled pteropods and heteropods at stations in the eastern Equatorial Pacific, North Pacific Central Water and the Tongue of the Ocean, Bahamas, was estimated using the instantaneous growth rate method. At all stations, pteropods were 3 to 9 times more abundant than heteropods and constituted 65 to 96% of aragonite production. Estimates of aragonite production ranged from 2.1 to 6.9 mg CaCO3 m−2 d−1. Using weighted averages based on two broad divisions of oceanic productivity, results were compared to reported aragonite fluxes measured with sediment traps. The data indicate that a source of alkalinity other than the dissolution of pteropod and heteropod aragonite is needed to supply the majority of a published estimate of CaCO3 dissolution in the water column of the North Pacific.