The structure of the hypothetical copper-metallochaperone CopZ from Bacillus subtilis and its predicted partner CopA have been studied but their respective contributions to copper export, -import, -sequestration and -supply are unknown. ΔcopA was hypersensitive to copper and contained more copper atoms cell−1 than wild-type. Expression from the copA operator-promoter increased in elevated copper (not other metals), consistent with a role in copper export. A bacterial two-hybrid assay revealed in vivo interaction between CopZ and the N-terminal domain of CopA but not that of a related transporter, YvgW, involved in cadmium-resistance. Activity of copper-requiring cytochrome caa3 oxidase was retained in ΔcopZ and ΔcopA. ΔcopZ was only slightly copper-hypersensitive but ΔcopZ/ΔcopA was more sensitive than ΔcopA, implying some action of CopZ that is independent of CopA. Significantly, ΔcopZ contained fewer copper atoms cell−1 than wild-type under these conditions. CopZ makes a net contribution to copper sequestration and/or recycling exceeding any donation to CopA for export.