A cluster of cases of lymphadenitis occurred in Dublin following vaccination with a newly introduced Copenhagen 1331 strain of Bacille Calmette-Guerin (BCG) vaccine during 1989. All cases of BCG lymphadenitis presenting to paediatric surgical clinics over an 11-year period were reviewed to determine the optimum treatment for this problem. Seventeen patients are included, 16 of whom received vaccine in the newborn period; 1 received BCG at 8 months. Nine were treated by initial operation, 6 with antituberculous drugs, and 2 were observed without specific therapy. All but 1 of the medically treated patients and both patients who received observation only required operation for failure to resolve or progression of disease. The best results were obtained with excision and primary closure. We conclude that although sponteneous resolution occurs in a majority of all cases of BCG lymphadenitis in infants, in those patients with more severe disease who require surgical referral, a short trial of anti-microbial therapy is indicated. Patients who fail to improve or develop complications are then best treated by surgical excision of the involved nodes.