The gene encoding the human basic fibroblast growth factor (hbFGF) has been already chemically-synthesized and cloned in pET-3a expression vector (Pasteur Institute of Iran). In the present study, we compared the level of expression of this synthetic hbFGF and its related cDNA in Escherichia coli. The pBR322-cDNA of hbFGF supplied by Dr. Seno (from Molecular Biology Dept, Okaido prefectural university, Japan), was utilized to introduce two restriction sites (BglII and NdeI) in either ends of the gene by PCR. This PCR product was inserted into SmaI site of pUC18 plasmid (pUC-1003). This construct was inserted into BamHI site of pET-3a expression vector (pET-1004). A final construct for expression of the gene was also made (pET-1005). The level of expression of the synthesized gene was compared to that of the cDNA using SDS-PAGE, western-blotting or ELISA. The results showed that expression of the hbFGF cDNA was much higher than that of the related synthetic gene, (16 mg/l and 0.025 mg/l respectively). Although in designing the synthetic gene the “codon usage” of E. coli was considered, it seems that “codon usage” did not improve the level of expression of the gene as was expected.