Age-related differences in etiology were examined in 214 instances of mycobacterial cervical lymphadenopathy. In adults, Mycobacterium tuberculosis was isolated from 147 lymph nodes and "atypical" mycobacteria was isolated from seven nodes. In contrast, M tuberculosis was isolated from only five nodes from children while other mycobacteria were isolated from 55 nodes. Mycobacterium tuberculosis clearly preponderates as the cause of mycobacterial cervical adenitis in adults while other mycobacteria are the cause of most cervical adenitis in children. The preponderance of Mycobacterium avium-intracellulare in cervical adenitis in children contrasts with reports of Mycobacterium scrofulaceum as the most frequent causative agent in other geographic areas and may reflect either a change in causative agents or geographic differences. However, the finding of M tuberculosis in 8% of nodes indicates that other mycobacteria cannot be assumed to be the only cause of this disease in children.