Genomic DNA samples isolated from Fenneropenaeus chinensis (fleshy prawn; FP) and Palaemon gravieri (Chinese ditch prawn; CDP) collected in the West Sea, off the Korean Peninsula, at Buan, were PCR-amplified repeatedly. The sizes of the DNA fragments generated by seven different primers varied from 50 bp to 1,600 bp. We identified 358 fragments for the FP species and 301 fragments for the CDP species. There were 18 polymorphic fragments (5.03$\%$) for the FP species and 12 (3.99$\%$) for the CDP species. In total, 66 common fragments (average of 9.4 fragments per primer) were observed for the FP species and 44 fragments (average of 6.3 fragments per primer) were observed for the CDP species. The numbers of specific fragments seen for the FP species and CDP species were 38 and 47, respectively. The complexity of the banding patterns varied dramatically between the primers and the two species. In the FP species, a specific fragment of approximately 1,200 bp generated by primer OPB-04 exhibited inter-individual-specific characteristics that were indicative of DNA polymorphisms. Moreover, in the CDP species, a major fragment of approximately 550 bp generated by primer OPB-20 was found to be specific for the CDP. The average bandsharing value between the two prawn species was 0.421$pm$0.006, and ranged from 0.230 to 0.611. The dendrogram obtained using the data from the seven primers indicated seven genetic clusters: cluster 1, FLESHY 01, 02, 03, and 04; cluster 2, FLESHY 05, 06, and 07; cluster 3, FLESHY 08, 09, 10, and 11; cluster 4, DITCH 13, 14, 16, and 18; cluster 5, DITCH 12, 15, and 17; cluster 6, DITCH 19, 20, and 21; and cluster 7, DITCH 22. The genetic distance between the two prawn species ranged from 0.071 to 0.642. Thus, RAPD-PCR analysis revealed a significant genetic distance between the two prawn species. Using various arbitrary primers, RAPD-PCR may be applied to identify specific/polymorphic markers that are particular to a species and geographic population, and to define genetic diversity, polymorphisms, and similarities among shrimp species.