We experienced a case of infiltrating lobular carcinoma of the breast in the ascitic fluid. The patient was a 49 year-old woman who presented with a palable mass of 3 months duration in the left upper quadrant of the abdomen and abdominal distension. Five years ago, she had undergone left radical mastectomy with chemotherapy and radiotherapy for infiltrating lobular carcinoma of the breast. The ascitic fluid smears revealed singly scattered small round to elliptical cells, many of which were arranged in characteristic indian-file patterns consisting of 3 to 5 cells. The tumor cells had scanty cytoplasm, rare cytoplasmic vacuoles and marked chromatin clumping with small, but prominent nucleoli.