The lymph node biopsy may well be the most important surgical operation that the patient ever has. Recent advances in the immunological characterization of human lymphocyte sub-populations, and the use of selected cytochemistry techniques have enabled increased understanding of the pathogenesis of malignant lymphomas, as well as providing more precise categorization of the cell of origin of many of these tumours. The fact is, however, that the vast majority of diagnoses of lymph node biopsies are made on morphological features observed at light microscopy level. The diagnosis and differential diagnosis of lymphomas, and particularly their distinction from benign conditions, are among the most frequent and most difficult problems in diagnostic histopathology. Whilst many of the principles enumerated in the text apply to all areas of surgical pathology, meticulous attention to detail is essential at all phases in the preparation of a satisfactory lymph node biopsy.