Fluorescence in situ hybridization (FISH) has become and indispensable tool in a variety of areas of research and clinical diagnostics. Many applications demand an approach for simultaneous detection of multiple target sequences that is rapid and simple, yet sensitive. In this work, we describe the synthesis of two new cyanine dye-labeled dUTP analogs, Cy3-dUTP and Cy5-dUTP. They are efficient substrates for DNA polymerases and can be incorporated into DNA probes by standard nick translation, random priming and polymerase chain reactions. Optimal labeling conditions have been identified which yield probes with 20-40 dyes per kilobase. The directly labeled DNA probes obtained with these analogs offer a simple approach for multicolor multisequence analysis that requires no secondary detection reagents and steps.