Outbreak of Bacillus Calmette-Guerin-associated lymphadenitis and abscesses in Jamaican children. An outbreak of axillary lymphadenitis and abscesses after Bacillus Calmette-Guerin (BCG) vaccination (Pasteur Paris, Batch N5122) occurred in 139 Jamaican children between January and July, 1988. The overall rate of this complication was 0.95%. The attack rate was 1.92% among the 0- to 6-week age group and 0.6% in the 7- to 52-week age group. Of 139 patients there were 77 males and 62 females and the mean age at presentation was 4 months. The mean size of the BCG scar, duration of healing and Mantoux reaction size differed significantly in patients compared with those of control infants (P less than 0.01). Mycobacterium bovis was isolated from 11 patients. Immunologically index patients and controls differed significantly only with respect to T lymphocyte subpopulation percentages and concanavalin A stimulation indices. Evaluation of the BCG vaccine did not reveal either increased potency or microbial contamination. We conclude that increased susceptibility to the Pasteur strain of BCG might have contributed to the increased incidence of complications in these Jamaican children and hence caution should be exercised in switching one vaccine for another as is often done in the developing countries. 