Specimens from 58 children with decubitus ulcers were cultured for aerobic and anaerobic bacteria. Aerobic bacteria only were present in 29 (50%) ulcers, anaerobic bacteria only were recovered in 5 (9%), and mixed aerobic and anaerobic flora were present in 24 (41%). A total of 132 isolates (79 aerobes, 53 anaerobes) were recovered, an average of 2.3 isolates per specimen (1.4 aerobes, 0.9 anaerobes). The smallest number of isolates was recovered in ulcers of the skull (1.7 per site), and the highest number of isolates was found in ulcers of the buttocks (4.1 per site). The predominant isolates were Staphylococcus aureus (25 isolates), Peptostreptococcus species (22), Bacteroides fragilis group (10), and Pseudomonas aeruginosa (7). Forty-two of the organisms isolated from 38 (66%) patients produced the enzyme β-lactamase. Most of the S aureus isolates were recovered from ulcers of the hand and the leg. Organisms that resided in the mucous membranes close to the ulcer predominated in the wounds next to these areas. Enteric gram-negative rods, group D streptococci, and B fragilis group predominated in ulcers of the buttocks. Group A streptococci, Haemophilus influenzae, Bacteroides melanino-genicus group, and Fusobacterium species were most frequently recovered in ulcers of the skull. The polymicrobial etiology of decubitus ulcers in hospitalized children and the association of bacterial flora with the anatomical site of the ulcer are demonstrated. © 1991.