Two proteins which have carbonate dehydratase (carbonic anhydrase, EC 4.2.1.1) activity were shown to be in the chloroplasts and in the cytosol of leaves of Brassica chinensis, Spinacia oleracea, and in variegated leaves of Tradescantia albiflora and Hedera canariensis. The chloroplastic enzyme is smaller than the one in the cytosol, as it runs farther on gradient polyacrylamide gels. It was separated from the other by isolation of chloroplasts of Brassica and Spinacia on sucrose density gradients; approximately half of the total activity was in the chloroplasts.