Phenazines produced by members of several bacterial genera are biologically active metabolites that function in microbial competitiveness, the suppression of soil-borne plant diseases and virulence in infectious disease. Despite recent progress towards understanding the biochemistry of phenazine synthesis, the key reactions leading to the formation of the heterocyclic scaffold common to all phenazine compounds remain obscure. Pseudomonas fluorescens 2-79 contains seven phenazine (phz) genes that encode components of the pathway for biosynthesis of phenazine-1-carboxylic acid. A central step in this pathway involves the condensation of two identical precursor molecules derived from chorismic acid and is catalysed by the product of the phzF gene. In this study, recombinant PhzF was purified and crystallized from PEG 4000/ammonium sulfate/sodium citrate pH 5.6. The crystals belong to space group P3(1)21 or P3(2)21, with unit-cell parameters a = b = 56.3, c = 156.4 A. They contain one monomer in the asymmetric unit and diffract to better than 1.7 A on synchrotron beamlines. Crystals of seleno-L-methionine-labelled PhzF have been obtained and SAD data are reported.