The low-level laser irradiation (LLLI) therapy for bone healing has attracted strong interest in the field of clinical implantology. It has been reported that LLLI on bony implant sites might have positive effects on the integration of implants. The biostimulatory effect of bone formation by LLLI has been investigated, however, very little is known about the molecular basis of biostimulatory mechanisms. Since LLLI will be useful to support implanttherapy, it is important to elucidate the mechanism of biostimulatory effect of LLLI on bone formation.<br/> We previously constructed a cDNA library of mouse osteoblastic cells (MC3T3-E1), which enhanced gene expression by LLLI using a subtracted gene cloning technology. In the present study, we analyzed the DNA nucleotide sequence of gene clones MCL-176. The nucleotide sequence of MCL-176 DNA insert was determined and assessed in the standard nucleotide-nucleotide BLAST homology-search using NCBI DNA databases. DNA nucleotide sequences of clone MCL-176 cloned DNA exhibited high homology with macrophage(migration) inhibitory factor (MIF) gene. Reverse-transcription real-time PCR analysis showed that MIF mRNA level was enhanced by LLLI. MIF is known as a cytokine that mediates inflammatory processes in a variety of tissues. Since it has been reported that MIF is also presented in osteoblasts and MIF modulates the proliferation of osteoblasts, MIF is involved in the growth of osteoblasts and bone tissue remodeling. Our findings suggest that LLLI may enhance MIF mRNA transcription of osteoblasts and play a role in the osseous metabolism.<br/>