The yellow fungal isolates inhabiting at the cereals (Hwang-Kuk, HK-fungi) were widely collected from the mejus and nuluks in Korea; the meju is a raw material for Korean traditional foods for soysauce and soypaste, and the nuluk is a raw material for Korean traditional rice wine. These isolates, well known as an Aspergillus oryzae producing amylase for Korean rice wine or producing protease for soybeans, were compared with Aspergillus species known. All isolates were microscopically observed to be a species of A. oryzae or its related, but to be difficult to be identified. Thus, RAPD-DNA techniques were applied for these isolates and analyzed with nummerical values using NT-system, or Ecological programs or Factorial analyses. Several common bands of RAPD-DNA in the 28 isolates were synthesized with the different OPD primers and speculated to be used for identification of HK fungi. The HK-fungi isolated were revealed to belong to the group of A. flavus previously defined. Particularly, the isolates collected from mejus were analyzed to be more closed to A. flavus, The species of A. flavus, A. oryzae and A. sojae were grouped at the values lower than those indicating the diversity of species. In other words, these three fungal species were not distinguishable and all isolates known as a HK-fungus were very closed to A. flavus, All isolates were not diversified at groupings of RAPD-DNA, and considered to be not the natural flora at the mejus or nuluks. The meju or nuluk having the above fungi as the fungal flora were speculated to be not termed "Korean traditional foodstuffs".The yellow fungal isolates inhabiting at the cereals (Hwang-Kuk, HK-fungi) were widely collected from the mejus and nuluks in Korea; the meju is a raw material for Korean traditional foods for soysauce and soypaste, and the nuluk is a raw material for Korean traditional rice wine. These isolates, well known as an Aspergillus oryzae producing amylase for Korean rice wine or producing protease for soybeans, were compared with Aspergillus species known. All isolates were microscopically observed to be a species of A. oryzae or its related, but to be difficult to be identified. Thus, RAPD-DNA techniques were applied for these isolates and analyzed with nummerical values using NT-system, or Ecological programs or Factorial analyses. Several common bands of RAPD-DNA in the 28 isolates were synthesized with the different OPD primers and speculated to be used for identification of HK fungi. The HK-fungi isolated were revealed to belong to the group of A. flavus previously defined. Particularly, the isolates collected from mejus were analyzed to be more closed to A. flavus, The species of A. flavus, A. oryzae and A. sojae were grouped at the values lower than those indicating the diversity of species. In other words, these three fungal species were not distinguishable and all isolates known as a HK-fungus were very closed to A. flavus. All isolates were not diversified at groupings of RAPD-DNA, and considered to be not the natural flora at the mejus or nuluks. The meju or nuluk having the above fungi as the fungal flora were speculated to be not termed 'Korean traditional foodstuffs'.