Fatty acid profiles were prepared for a range of strains representing all 14Xanthomonas campestrispathovars from the Gramineae. Profiles were complex, containing up to 40 acids, most of which were iso‐ and anteiso‐branched acids. Grouping of profile types generally correlated with pathovar, although pvstranslucens, hordei, cerealis, secalisandundulosacould not be differentiated. Pvsgraminis, arrhenatheri, poaeandphleiformed another profile type although there were some differences between the pathovars. Thesegraminisandtranslucensgroups had similar profiles but could usually be differentiated by the ratios of 15:0 iso/16:0 iso and 15:0 iso/15:0 anteiso fatty acid methyl esters. The other pathovars each had a very different profile type. Pvsoryzaeandoryzicolahad profiles which were very different from all others. Pv.vasculorumcomprised at least two distinct profile types. This did not correlate with host species or geographic distribution. Fatty acid profiling can be used to identify strains ofX. campestrispathovars from Gramin