Detection of Mycoplasma synoviae (MS) by culture and polymerase chain reaction (PCR) has been reported from commercial chicken farms in different provinces of Iran. In some reports the phylogenetic analysis of MS isolates based on 16S rRNA and variable lipoprotein hemagglutinin (vlhA) genes have been carried out. The PCR product containing partial 16S rRNA genes of Iranain isolates was sequenced, and compared with 16S rRNA gene of MS sequences which were available in GenBank. Variations, polymorphisms, and differences between nucleotides of all isolates were observed. Phylogenetic analysis of these sequences showed that all MS isolates from Iran were most closely related to sequences of MS from Brazil. Sequence analysis of the N-terminal end of the hemagglutinin encoding gene vlhA were also used as an alternative for the detection and initial typing of field strains of MS in commercial poultry. The results showed that there was a complete concordance between all Iranian isolates nucleotide sequence and the 5́-vlhA region sequence remained unchanged in all MS isolates and demonstrated differentiation between Iranian isolates and live commercial MS-H vaccine strain. More recently, the single-copy domain of the conserved region of vlhA gene in MS was sequenced, analyzed and verified to type MS field isolates in Iran and live vaccine MS-H strain. In addition, a restriction fragment length polymorphism (RFLP) method was established based on single nucleotide polymorphism that existed in all field isolates of Iran to differentiate between these field isolates and MS-H. This PCR-RFLP method allowed differentiating all MS field isolates from the vaccine strain.