Fibrous materials in some modern absorbent wound dressings have the ability to sequester and retain bacteria; however, this ability varies according to the nature of the fibres. We studied the bacterial retention capacity of alginate and carboxymethylcellulose dressings, using an infected skin ulcer model on the backs of rats. Wound surfaces were inoculated with either Staphylococcus aureus or Pseudomonas aeruginosa at a concentration of 1.5 x 10(6) colony-forming units per wound. AQUACEL; Hydrofiber;, Kaltostat; or Sorbsan; were applied to the contaminated wounds for 12 h. Each dressing was then divided into two pieces. Total viable bacterial count within the dressing was calculated using one piece, and bacterial count released from the dressing into physiological saline was determined using the other piece, enabling bacterial retention rate to be calculated. Bacterial counts in tissue were also determined. Each dressing was tested on each of 10 wounds contaminated with each bacterium. Statistical analyses were performed using one-way analysis of variance (ANOVA) for replicated measures combined with Duncan's multiple comparison test. AQUACEL; Hydrofiber; dressing was most effective in its ability to retain both Staphylococcus aureus and Pseudomonas aeruginosa (p < 0.05). Bacterial counts in tissue showed no significant change with respect to pathogen or the type of dressing used. It can be concluded that the bacterial retaining ability of AQUACEL; Hydrofiber; dressing was found to be significantly higher than that of alginate dressings in an infected animal wound model.