Objectives: To clone genes specifically expressed in the placenta of patients with preeclampsia. and to explain the mechanism in the etiopathology of preeclampsia. Methods: The placentae of preeclamptic and normotensive subjects with pregnancy were used as models, and the eDNA Library was constructed and 20 differentially expressed fragments were cloned after a new version of PCR-based subtractive hybridization. The false positive clones were identified by reverse dot blot analysis. With one of the obtained gene taken as the probe, the placentas of 10 normal pregnant women and 10 preeclamptic patients were studied by using dot hybridization methods. Results: Six false positive clones were identified by reverse dot blot, and the rest 14 clones were identified as preeclampsia-related genes. These clones were sequenced, and analyzed with BLAST analysis system. Eleven of 14 clones were genes already known, among which one belongs to necdin family; the rest 3 were identified as novel genes. These 3 genes were acknowledged by GenBank, with the accession numbers AF2322 16, AF2322 17, AF233648. The results of dot hybridization using necdin gene as probe were as follows: (1) There was this mRNA in the placental tissues of normal pregnancy as well as in that of preeclampsia. (2) The intensity of transcription of this mRNA in the placental tissues of preeclampsia increased significantly compared with that of the normal pregnancy (P＜0.05). Conclusions: This study for the first time reported this group of genes, especially necdin-expressing gene, which are related to the etiopathology of preeclampsia. In addition, the overtranscription of necdin gene has been found in preeclampsia. it is helpful in further studies of the etiology of preeclampsia. Objectives: To clone genes specifically expressed in the placenta of patients with preeclampsia. And to explain the mechanism in the etiopathology of preeclampsia. Methods: The placentae of preeclamptic and normotensive subjects with pregnancy were used as models, and the eDNA Library was constructed and 20 differentially expressed fragments were cloned after a new version of PCR-based subtractive hybridization. The false positive clones were identified by reverse dot blot analysis. With one of the obtained genes taken as the probe, the placentas of 10 normal pregnant women and 10 preeclamptic patients were studied by using dot hybridization methods. Results: Six false positive clones were identified by reverse dot blot, and the rest 14 clones were identified as preeclampsia-related genes. These clones were sequenced, and analyzed with the BLAST analysis system. were genes already known, among which one belongs to necdin family; the rest 3 were identified as novel genes. These 3 genes were confirmed by GenBank, with accession numbers AF2322 16, AF2322 17, AF233648. The results of dot hybridization using necdin gene as probe were as follows: (1) There was this mRNA in the placental tissues of normal pregnancy as well as in the of preeclampsia. (2) The intensity of transcription of this mRNA in the placental tissues of preeclampsia increased significantly compared with that of the of the normal pregnancy (P <0.05). Conclusions: This study for the first time reported this group of genes , particularly necdin-expressing gene, which are related to the etiopathology of preeclampsia. In addition, the overtranscription of necdin gene has been found in preeclampsia. it is helpful in further studies of the etiology of preeclampsia.