The serial analysis of gene expression (SAGE) technique is an important tool for genome-wide gene expression analysis. However, the requirement of a large amount of mRNA for the analysis and the difficulties in generating high-quality tag and ditag fragments for the construction of a SAGE li- brary often interfere with the successful performance of the SAGE technique. We de- veloped two procedures to solve these is- sues: (i) introducing low-cycle PCR ampli- fication of the 3′ cDNA before the BsmFI digestion of the 3′ cDNAs and (ii) gel puri- fyingtheBsmFI-releasedtagfragmentsbe- fore ditag formation. These modifications provide a large quantity of initial 3′ cDNAs and high-quality tags and ditags for the construction of SAGE libraries.