Abdominal sonography is now the most frequently used screening method for the detection of abdominal lymph node enlargement. For proper classification, size, localisation and infiltration pattern must be known. The definitive determination whether lymph nodes are benign or malignant cannot be made by the size of the lesion alone. The localisation (parietal/visceral) of enlarged lymph nodes has been shown to be of significance in the staging of abdominal carcinomas. Different infiltration patterns (diffuse small nodular, focal small nodular, focal large nodular, bulky formations) show the broad spectrum of abdominal lymphomas detected by ultrasound. Knowledge of these different infiltration patterns together with clinical information often helps to discriminate between lymph node enlargement caused by inflammation, metastasis, or malignant lymphoma. The definitive diagnosis is made via laparotomy, ultrasound guided biopsy or sonographic follow-up studies.