Vectorette polymerase chain reaction (PCR) is a method designed to amplify DNA when the sequence of one end of the target DNA is unknown (1,2). This technique, therefore, gives a handle on unknown sequence, which flanks DNA that has already been characterized, or sequenced. The vectorette method was conceived and patented in 1988 when it was used to sequence the termini of YAC clone inserts (1), as well as to undertake genomic walking (2). Other applications have been developed, including sequencing of cosmid insert termini, mapping of promoters, and/or introns in genomic DNA from cDNA subclones, sequencing of large clones without subcloning, mapping of regions containing deletions, insertions, and translocations. Vectorette PCR has also been adapted to clone full-length cDNA and determine the 5′ and 3′ ends of mRNAs (3).