A DNA renaturation method in gel was used to detect amplified DNA fragments in eight gastric cancer cell lines, KATO-III, OKAJIMA, SCH, MKN1, MKN7, MKN28, MKN45 and MKN74 cells, and tissues of three metastases of gastric cancers to lymph nodes. There were amplified DNA sequences in three gastric cancer cell lines. Judging from the intensities of the bands, HindIII-digested DNA fragments were amplified several hundred times in the KATO-III and MKN7 cell lines. DNA from OKAJIMA cell line contained multiple bands with less intensity. KATO-III cells were found to contain a homogeneously staining region in chromosome 11.