To discover new genes in a throughput manner,the cap-trapper method published previously was optimized for raising the efficiency in the construction of full-length cDNA library. Using the optimized protocol,we successfully constructed a full-length cDNA library of Aegilops speltoides,which contained 3.0 x 10(6) clones and more than 99% of plaques were recombinant phages. Sequence analysis results indicated that more than 89% of the clones were full-length.