We have already reported the cloning of one phosphoenolpyruvate carboxylase kinase gene from Arabidopsis thaliana (Hartwell et al. 1999, Plant Journal 20, 333–342), hereafter termed PPCK1. A second putative phosphoenolpyruvate carboxylase kinase gene (PPCK2) was identified in the Arabidopsis genome. The corresponding cDNA was amplified from flower tissue by reverse transcriptase (RT)-polymerase chain reaction (PCR). This cDNA was transcribed and translated in vitro. The translation products possessed high phosphoenolpyruvate carboxylase kinase activity, confirming the identity of the PPCK2 gene. The expression of both phosphoenolpyruvate carboxylase kinase genes was examined by RT-PCR. PPCK1 is mainly expressed in rosette leaves whereas PPCK2 is expressed in flowers and, at a lower level, in roots and cauline leaves. Light increased the expression of PPCK1 in rosette leaves and that of PPCK2 in flowers. The expression of both genes in an Arabidopsis cell culture was increased by treatment with cycloheximide. The data suggest that the two genes may have different roles in tissue-specific regulation of phosphoenolpyruvate carboxylase.