Gestational trophoblastic diseases comprise a group of interrelated neoplasms, including partial hydatidiform mole, complete hydatidiform mole, placental site trophoblastic tumor and choriocarcinoma. During the past few years the molecular and biochemical characterization of distinct gene expression repertoires and/or the specific products has emphasized the functional importance of differentially expressed genes in establishing normal or tumoral phenotypes. A search for genes involved in the pathogenesis and prognosis of gestational tumors applying Differential Display techniques allowed us to isolate several differentially expressed cDNA fragments. Previously, we reported that three of these fragments corresponded to mitochondrial transcripts with diminished expression in both benign and malignant trophoblastic tumors (Placenta, 22: 220, 2001). In addition, the differential expression of decorin, hnRNP A1 and ribosomal L27 was communicated. In the present report, we extended the molecular charac terization to other three cDNA fragments. Two of them were upregulated in JEG-3 choriocarcinoma cell line and the other one was upregulated in normal early placenta. Cloning experiments and sequence data showed that two of them corresponded to known mRNA: light ferritin and ribosomal L26. One of the sequences corresponded to transcript of yet-unidentified gene. A search for a full length sequence is currently performed. Taken together, these data demonstrate that significant changes in the transcription of nuclear and mitochondrial genomes is associated with the phenotypic alteration present in GTDs.