The PCR-Select cDNA Subtraction Kit offers an efficient method for selectively amplifying differentially expressed genes—those genes expressed in one mRNA population but reduced or absent in another (Akopyants, 1998; Jin, 1997; Diatchenko, 1996; Diatchenko, 1998). This method is particularly well-suited for the identification of target cDNAs that correspond to rare transcripts, which are typically the most difficult to obtain. In contrast to other methods that require physically separating single-stranded and double-stranded cDNAs, the PCR-Select method allows the exponential amplification of only the desired sequences. This method offers many significant advantages: