A series of DNA primers specific for human brain myelin basic protein (MBP) gene was designed and synthesized. MBP cDNA fragment about 600bp in length was amplified from human brain cDNA library by using polymerase chain reaction (PCR) with the specific primers P₁ and P₂. The recovered PCR product was flushed by klenow fragment and inserted into pGEM-3Zf (+) vector pretreated with SmaⅠand calf intestinal alkaline phophatase. The recombinant plasmid was used to trans-form competent cell JM 109. The positive colonies were directly screened on indicator plates. The recombinant plasmid DNA and insert fragment isolated from four positive colonies were analyzed by digestion with EcoR Ⅰ，Kpn Ⅰ and Taq Ⅰ.The different coding sequences including MBP exon Ⅰ—Ⅶ, Ⅰ—Ⅲ，Ⅲ—Ⅶ and Ⅰ—Ⅴ were amplified from these clones with their corresponding nested sets of primers respectively. These results show that these cDNA clones contain full-length coding sequence for 21.5kD human MBP.