A cDNA library derived from antigenically homogeneous bloodstream stage Trypanosoma brucei brucei was screened with an antiserum directed against the variant surface antigen (VSA) using an enzyme-linked filter immunoassay. Several recombinant clones were detected and the clone giving the most intense reaction was further analyzed. It contained a VSA-specific cDNA insert and synthesized a protein of the expected molecular weight bearing VSA determinants. The nucleotide sequence of the insert was determined and shown to have the unusual codon bias characteristic of T. brucei VSAs, frequently employing codons specifying tRNAs rare in Escherichia coli. These results indicate that a codon bias very different from that of E. coli does not preclude the expression of a cloned sequence to detectable levels in this heterologous host.