A new method of DNA analysis has been used for the determination of androgenesis as a cause of complete hydatidiform mole. This method, using a minisatellite core probe, requires only a small amount of DNA and detects the restriction fragment length polymorphisms (RFLPs) due to allelic differences in the number of tandem repeats containing the core sequence. Southern blot hybridization showed an individual-specific DNA fingerprint, and each polymorphic band in molar tissues could be identified as being of paternal, but not maternal, origin. Some polymorphic bands of paternal DNA were not observed in molar tissues, indicating that endoreduplication of a normal haploid sperm or fertilization by dispermy to an anuclear oocyte with no effective genome could be the cause of complete hydatidiform mole. This method is sufficiently reliable and rapid that differential diagnosis could be made between complete hydatidiform mole, partial mole and hydropic change.