In order to investigate the diversity of bacterial community in the mud flat of Sunchon Bay, Chunnam province, diversity of amplified 16S rDNA was examined. Total DNA was extracted from sediment soils and 16S rDNAs were amplified using PCR primers based on the universally conserved sequences in bacteria. Clonal libraries were constructed and 111 clones were examined by amplified rDNA restriction analysis (ARDRA) using HaeIII. Clones were clustered based on restriction patterns using computer program, GelCompar II. One hundred different RFLP types were detected from 111 clones. The 20 clones were selected and sequenced according to dendrograms derived from ARDRA, to cover most of the bacterial diversity in the clone libraries. None of the clones were identical to any representatives in the Ribosomal Database Project small subunit RNA databases and GenBank. All sequences showed between 77 and 96.8% similarity to the known 16s rRNA sequence from cultured organisms. The 20 clones sequenced fell into seven major lineages of the domain Bacteria: alpha-, delta-, gamma-Proteobacteria, low G+C Gram positive bacteria, high G+C Gram positive bacteria, Sphingobacteria (Cytophaga) and Cyanobacteria (chloroplast). Among the clones, the Proteobacteria were dominant.