We isolated several mutants of Arabidopsis thaliana that accumulated less anthocyanin in the plant tissues, but had seeds with a brown color similar to the wild-type. These mutants were allelic with the anthocyaninless1 mutant that has been mapped at 15.0 cM of chromosome 5. We made fine mapping of anl1 locus and determined that ANL1 locates between the nga106 marker and a marker designed on the MKP11 clone. About 70 genes were located between these two markers, including three UDP-glucose:flavonoid-3-O-glucosyltransferase like genes and a glutathione transferase gene (TT19). A mutant of one of the glucosyltransferase genes (At5g17050) did not compliment the anl1 phenotype, showing that the ANL1 gene encodes UDP-glucose:flavonoid-3-O-glucosyltransferase. ANL1 was expressed in all the tissues examined, including rosette leaves, stems, flower buds and roots. ANL1 was not regulated by TTG1.