We have analyzed DNA of EUGLENA: gracilis for the presence of the unusual minor base beta-D-glucosyl-hydroxymethyluracil or J, thus far only found in kinetoplastid flagellates and in DIPLONEMA: Using antibodies specific for J and post-labeling of DNA digests followed by two-dimensional thin-layer chromatography of labeled nucleotides, we show that approximately 0.2 mole percent of EUGLENA: DNA consists of J, an amount similar to that found in DNA of Trypanosoma brucei. By staining permeabilized EUGLENA: cells with anti-J antibodies, we show that J is rather uniformly distributed in the EUGLENA: nucleus, and does not co-localize to a substantial extent with (GGGTTA)(n) repeats, the putative telomeric repeats of EUGLENA: Hence, most of J in EUGLENA: appears to be non-telomeric. Our results add to the existing evidence for a close phylogenetic relation between kinetoplastids and euglenids.