This study determines the nature of microbial wound colonization in 28 patients with large burns admitted to the Burn Centre, Haukeland University Hospital, Bergen. Altogether, 748 swabs were taken in 141 sampling procedures. A total of 414 microbial isolates were detected and their resistance patterns to a variety of systemic antimicrobial agents determined. The most frequent isolates were coagulase-negative staphylococci (21.5 per cent) and Staphylococcus aureus (14 per cent), followed by Enterococcus species (11.3 per cent), Pseudomonas aeruginosa (10.9 per cent) and Candida species (9.7 per cent). Forty-one per cent of the enterococci and 36 per cent of the coagulase-negative staphylococci were resistant to the aminoglycosides routinely given in conjunction with surgery in our ward. Only four of the 89 strains of coagulase-negative staphylococci were insensitive to methicillin, and no Staph. aureus were methicillin resistant. The time-related changes of burn wound colonization showed that on admission and during the first week, staphylococci and alpha-haemolytic streptococci were dominant. During the next weeks, these bacteria were gradually superceded by enterococci, gram-negative opportunists (mainly Pseud. aeruginosa, Acinetobacter calcoaceticus and Escherichia coli) and Candida species. The nature of microbial wound colonization and how the flora changes with time should be taken into consideration by those treating thermally injured patients.