In the present study, cDNA encoding molt..inhibiting hormone ( MIH) was amplified from the total RNA of eyestalk neural ganglia of the mud crab, Scylla serrata, by means of reverse transcription polymerase chain reaction( RT..PCR) with degenerate oligonucleotide primers based upon the homology DNA sequence of MIH from other Brachyuraspecies. Then the fragments were cloned with pUCm..T vector and sequenced. The total length of 316bp sequence was obtained that encoded full..length mature peptide of 78 amino acids and partial signal pept ide. According to the search results of GenBank databases, the cDNA fragment and the deduced amino acid sequence of mature peptide share 79% ~ 91% identity with that of other species in the Brachyura. Expression of MIH was detected in the eyestalk, brain, midgut gland and muscle tissues examined by RNA dot hybridization. The results indicated that the MIH was expressed only in the eyestalk and brain not in other tissues.