Nucleolar organizer regions (NORs) are loops of ribosomal DNA (rDNA) encoded for ribosomal RNA (rRNA) production. Some special proteins associated with NORs are termed NOR associated proteins or AgNORs. Attention has recently been drawn to application of a silver colloid technique (AgNOR technique) for demonstrating the AgNORs as an index of cell proliferation. In this study AgNOR technique was applied to imprint preparations of 25 gastrointestinal system malignant tumors and 25 normal gastrointestinal mucosas. "A significant difference in the mean number of AgNORs per nucleus was found between malignant tumor and normal mucosa (p< 0.001). These results suggest that AgNOR staining technique may be useful in the field of gastrointestinal system tumor cytopathology.