In order to determine the p53 status of gestational trophoblastic neoplasia, 24 cases of molar pregnancies and two choriocarcinoma cell lines (JAR and JEG-3) were evaluated for the presence of mutations. The evaluation involved the whole coding sequence (i.e. exons 2-11) of the p53 gene with polymerase chain reaction (PCR) amplification of genomic DNA, followed by single strand conformation polymorphism (SSCP) and sequencing. Only one case of hydatidiform mole was found to have a missense point mutation (codon 295, CCT-->CTT, i.e. proline to leucine) of the p53 gene. The results suggest that p53 mutation is rarely involved in the pathogenesis of gestational trophoblastic neoplasia.