In this study, we performed the differential display technique to identify genes specifically expressed in human choriocarcinoma cell lines (JEG-3, JAR and BeWo) and normal placental term cells. Few differences were found among the expression profiles of the three choriocarcinoma cell lines and most of the differentially expressed genes were detected in normal term placenta. A total of 36 cDNA fragments were isolated and analysed. Of these, 19 sequences corresponded to regions in the human genome coding for potential novel genes. We confirmed by RT-PCR, the placental mRNA expression of three selected new human genes, on chromosomes 16q12, 9q32 and 6q22. The other 17 sequences showed high similarity to known human genes (like PSG3, FN1, PAI-2). Interestingly, the functions of five known proteins (from genes IK, TRA-1, HERPUD1, UBA-2, and TRAP240) have not yet been well characterized in placenta tissue. In addition, new alternative spliced mRNAs were detected for IK, TRAP240 and PLAC3 genes. The differential expression of the PAI-2 gene among the choriocarcinoma cell lines was also confirmed. The genes identified in this analysis will be of interest for future studies regarding both a better understanding of the biology of the trophoblast cell and the formation of placental tumors.