OBJECTIVE: To date early predictors for the development of persistent gestational trophoblastic disease (PGTD) after evacuation of a complete hydatidiform mole were not known. The purpose of this study was to investigate whether there is a correlation between oncogene expression and PGTD after evacuation of molar pregnancy. METHODS: The expression of c-myc, c-ras, c-erb B-2 oncogene and p53 gene product in paraffin-embedded trophoblastic tissues using immunohistochemical staining were investigated retrospectively. We compared 20 cases of PGTD group with 20 cases of spontaneous regression group after molar evacuation. RESULTS: Expression of p53 gene was in 25% of regression group while it was detected in 15% of PGTD group. The c-myc, c-ras, c-erb B-2 oncogene product was detected in 80%, 20%, 40% of regression group while it was detected in 75%, 15%, 65% of PGTD group respectively. CONCLUSION: This result showed that correlation between c-myc, c-ras, c-erb B-2 and p53 gene product expression and PGTD is not significant.