Methicillin resistant Staphylococcus aureus strains (MRSA) have become increasingly prevalent as pathogenic organisms, especially in burn wounds, with an associated mortality of 20-40% among those clinically infected. Mupirocin ointment, a new topical antibiotic, has proved in vitro and in vivo to be highly effective in the treatment of MRSA infections. A modified Walker burn wound model was used to define the rate of trans-eschar penetration, biodynamic availability and bactericidal efficacy of 2% mupirocin ointment in established MRSA burn wound infection. In-vitro penetration trials confirmed the effective diffusion of mupirocin through 1.5 mm eschar within 2 h. A single topical application of mupirocin resulted in a 98.3% (5.67 x 10(8) cfu/g of tissue--1.0 x 10(7) cfu/g of tissue) reduction in intra-eschar viable organisms within 36 h post application. A second topical application of mupirocin at 24 h resulted in a total reduction of 99.6% in viable intra-eschar organisms (1.85 x 10(8) cfu/gram of tissue--6.76 x 10(5) cfu/g of tissue). It is concluded that mupirocin is highly effective in controlling MRSA burn wound infection and should be applied topically every 24 h.