In order to isolate and screem tissue-specific genes of human nasopharynx and new tumor suppressor genes of nasopharyngeal carcinoma(NPC),a directional cDNA library from human embryo nasopharyngeal epithelia was constructed by SMART(switching mechanism at 5′ end of RNA transcript) technique. The total RNA and mRNA were separated from primary cultural human embryo nasopharyngeal epithelia and the frist-strand cDNA was synthesized through reverse transcription by a modified oligo(dT) primer(contained sfiⅠB site) while the SMART oligonucleotide (contained sfiⅠA site) was utilized as a template so that the first-strand cDNA could be extended over the 5′end of mRNA. The double-strand cDNA was amplified by LD-PCR(long-distance PCR) with the above two primers and then digested by sfiⅠ(ⅠA & ⅠB) restriction enzyme.After cDNA size fractionation through CHROMASPIN column,the double-strand cDNA was ligated into the sfiⅠ-digested λTripIEx2 vector and then the recombinant DNA was packaged in vitro. The unamplified human embryo nasopharynx cDNA library consists of 1.0×10⁶ independent clones in which the percentage of recombinant clones is about 96%.The titer of the amplified cDNA library is 7.8×10⁹ pfu/ml and the average exogenous inserts of the recombinants is 1.2 kb.The full-length cDNA of NAG4, a candidate tumor suppressor gene related with nasopharyngeal carcinoma, was amplified in the cDNA library by PCR. These results show that the human embryo nasopharynx cDNA library has an excellent quality and lays solid foundation for screening and cloning new tumor suppressor genes of nasopharyngeal carcinoma and tissue-specific genes of human nasopharynx.