Objective: To investigate Echinococcus (E.) granulosus genotypes as the causative agents of hydatidosis in humans in the southwest of Iran (Khuzestan province). Methods: In this study, isolates of 80 archived human paraffin embedded hydatid cysts were collected from pathology laboratories in Ahvaz city, Khuzestan province. DNA was extracted and examined by nested-PCR of ribosomal DNA (rDNA) intal transcribed spacer 1 (ITS1), and PCR-RFLP. In addition, the sequences of fragments of genes coding for Cox space1 and NADH dehydrogenase 1 (ND1) were also examined. Results: Of the 80 paraffin samples, 44 (55.0％) were from the liver, 27 (33.8％) from the lung, and the rest from other organs. The amplified hydatid genomic DNA showed that the cysts were E. granulosus strains. The results of PCR-RFLP and sequencing analysis revealed the presence of G1 genotype (sheep strain) in all human isolates. Furthermore, no camel strain (G6) was detected among all samples in the regions studied. Conclusions: The molecular findings indicate that the predominant genotype involved in E. granulosus transmission in southwest of Iran is the common sheep strain (G1), which occurs in human populations. These results may have important implications for hydatid disease control in the studied areas.