DNA fingerprints are generated using probes that hybridize to hypervariable minisatellites, also known as variable number tandem repeat loci. Cloned minisatellites have served as the predominant source of DNA fingerprinting probes. A short segment within the repeat units of minisatellites, called the "core" sequence, is highly conserved within a family of related minisatellites, thereby allowing a single-cloned minisatellite to cross-hybridize to 20 to 40 other minisatellites. In this article, we describe a method for the synthetic preparation of polymeric core sequence probes for DNA fingerprinting. Unlike "monomeric" oligonucleotide probes, the polymeric probes mimic the tandem-repetitive structure of minisatellites, and thus each probe molecule can potentially form many sites of hybridization with a target minisatellite. The synthetic probes are cloned into plasmid DNA to provide a perpetual source of probe material.