Four tetramethylindo(di)carbocyanine-derived carboxylic acids have been prepared using a modified one-pot procedure for the dye assembly. The acids were converted into oxysuccinimide esters and phosphoramidite reagents. The efficiency of the reagents in the labeling of oligonucleotides and proteins has been demonstrated. © Wiley-VCH Verlag GmbH & Co. KGaA, 2008.