In fresh water planarian Dugesia japonica, two genes encoding POU-domain proteins, DjPOU1 and DjPOU2, have been identified by polymerase chain reaction (PCR). Their POU-domains are strikingly similar to class III POU-domains in mammals, frog, insects and nematode. The full-length cDNA of DjPOU1 has been cloned and sequenced, which revealed that it codes for a protein of 559 amino acids. The accumulation of DjPOU1 mRNA is two or three times more in anterior region of worm containing a brain, than the other regions, and decreases during regeneration after amputation.