In this study, we tried to find out the cytological relevance of cannibalism as a dependable feature of malignancy in effusion and urine cytology. We randomly selected a total of 40 cases consisting of 10 each of malignant effusion, benign effusion, malignant urine samples, and benign urine samples. These smears were assessed for the presence of cell cannibalism. The number of cannibalistic cells/100 tumor cells was counted. The cannibalistic cells were seen more commonly in malignant effusion cases (3.4/100 cells) compared with malignant urine cases (2/100 cells). There was not a single cannibalistic cell in benign conditions. The finding of an increased number of cannibalistic cell was highly significant in malignant versus benign samples (P > 0.0000, Student's t‐test). The present study highlights the significance of cannibalism in malignant urine and effusion cytology. We suggest that cell cannibalism is a dependable cytological feature of malignancy. Diagn. Cytopathol. 2003;28:86–87. © 2003 Wiley‐Liss, Inc.