Atypical mycobacterial (AMB) infection is an important cause of lymph node enlargement in children. Over the period, January 1992 to December 1993, 17 patients with lymphadenitis because of AMB infection were treated at the Royal Hospital for Sick Children in Glasgow. These case notes of the patients were reviewed. The mean age at presentation was 5.37 years (range 1.5-10.6 years). The patients had a short history (1-11 weeks) of unilateral single focus, usually cervicofacial (16/17), disease. The tuberculin skin test was not helpful in diagnosis (negative in 14/15). Primary excision was curative (11/11). Incision and drainage of an abscess or drainage with partial excision led to chronically discharging sinus in all cases (6/6). AMB were not always seen on staining (11/17) of drained or excised material and cultures were negative in eight cases. The diagnosis in the remaining patients was made on the basis of clinical features and particular histopathological patterns. We are currently assessing the use of polymerase chain reaction (PCR) techniques for making the diagnosis in non-cultured cases.