Understanding genetic structure and status of genetic variation of Fasciola hepatica isolates from different hosts, has important implications on epidemiology and effective control of fasciolosis. Random amplified polymorphic DNA (RAPD-PCR) was used to study the genetic variation of F. hepatica in sheep and cattle. DNA was extracted from adult helminthes removed from livers of each infected animal in slaughterhouse at East-Azerbaijan province, North-West of Iran. DNA template amplified by the polymerase chain reaction, using three oligonucleotide decamers with arbitrary DNA sequences as primers. RAPD patterns showed the specific but different pattern DNA patterns for each primer. The intraspecific similarity coefficient within two isolates of F. hepatica was ranged between 69 to 100%. Present findings showed that the interspecific genetic distance was higher than intraspecific genetic distances (19-47% compares to 0-19%). Pair wise similarity matrices generated from each isolates-primer combination were totaled and the similarity coefficient between strains were calculated both manually (Nei and Li method) and software analysis (Free-Tree-Freeware program). The inferred phylogenetic tree on the fingerprinting of these isolates clearly demonstrated the existence of population genetic diversity sub structuring within F. hepatica of sheep and cattle of Iran, raising interesting questions on the host specificity, epidemiology (e.g., zoonotic transmission) and ecology of this fluke. RAPD-PCR is useful for both individual identification and epidemiological investigations in endemic regions.