Abstract: Objective To carry out a clinical investigation and gene analysis of one pedigree with multiple endocrine neoplasia type 2A(MEN2A). Methods Carried out a clinical investigation of one MEN2A family,which has 24 members including the proband.The DNAs of the 16 members from the family were extracted from blood leukocytes,PCR and gene sequencing of PCR products by an automated DNA sequencer were applied to scan the exonl0 and 11 of the RET proto-oncogene. Results 1、The pedigree of this index case had one patient with multiple endocrine neoplasia type 2A,who refused to be phlebotomized for examining;Three doubtful patients had died,so could not have the gene analysis;Genetic screening identified the same mutation in a family member,who then died with chest distress and pallor suddenly at home.2、A missense mutation of TGC (Cys) to CGC (Arg) at codon 634 in exon 11 of the RET proto-oncogene was detected in the index case and a family member. Conclusion The mutation (C634R) is detected in the family with MEN2A.Early RET mutation analysis should be performed routinely in all MEN2A, and screening methods may be used in analyzing familymembers at risk.