Biotin deoxyuridine 5'-triphosphate (dUTP) and digoxigenin dUTP are the labels most commonly used in comparative genomic hybridization (CGH). The relative infrequent use of direct fluorochrome-labeled nucleotides in CGH is related to the lower sensitivity they provide. Here we report the evaluation of two fluorochrome-conjugated nucleotides that have not been previously used in CGH (lissamine-5-dUTP and fluorescein-N6dATP) and show that this direct label combination performs at least as well as the indirect biotin/digoxigenin pair.