The Plasmodium knowlesi circumsporozoite (CS) gene is expressed in Escherichia coli directly from a parasite genomic DNA fragment, using promoter and ribosome-binding site (RBS) sequences present in this fragment. Transcription of the CS gene in E. coli is directed by tandem Plasmodium bacterial-like promoter elements located within the 0.5-kb EcoRI-HindIII fragment roughly 2.5 kb 5' from the CS gene within the 11-kb EcoRI parasite genomic DNA fragment. No readthrough from vector promoters or fortuitous promotion from plasmodial A + T-rich sequences was observed. The endogenous Plasmodium promoter of the CS gene does not seem to be recognized by E. coli RNA polymerases. Two tandem E. coli-recognized promoters are relatively strong judging by their ability to drive the bacterial chloramphenicol acetyl-transferase (CAT) gene. Translation of the message must be achieved by utilising an AAGAA sequence 4 bp 5' from the ATG initiation codon as RBS.