Summary Infection is the likeliest single cause of delayed healing in healing of chronic open wounds by secondary intention. If neglected it can progress from contamination to colonization and local infection through to systemic infection, sepsis and multiple organ dysfunction syndrome, and it can be life-threatening. Infection in chronic wounds is not as easy to define as in acute wounds, and is complicated by the presence of biofilms. There is, as yet, no diagnostic for biofilm presence, but it contributes to excessive inflammation - through excessive and prolonged stimulation of nitric oxide, inflammatory cytokines and free radicals - and activation of immune complexes and complement, leading to a delay in healing. Control of biofilm is a key part of chronic wound management. Maintenance debridement and use of topical antimicrobials (antiseptics) are more effective than antibiotics, which should be reserved for treating spreading local and systemic infection. The continuing rise of antimicrobial resistance to antibiotics should lead us to reserve their use for these indications, as no new effective antibiotics are in the research pipeline. Antiseptics are effective through many mechanisms of action, unlike antibiotics, which makes the development of resistance to them unlikely. There is little evidence to support the theoretical risk that antiseptics select resistant pathogens. However, the use of antiseptic dressings for preventing and managing biofilm and infection progression needs further research involving well-designed, randomized controlled trials. What's already known about this topic? Infection is the most likely cause of stalled healing in chronic wounds. Infection in chronic wounds is a clinical decision-making process; a diagnostic would be useful for practitioners. Presence of biofilm cannot be detected clinically and a diagnostic is needed. What does this study add? Presence of biofilm is the likely cause of persistent infection and requires maintenance debridement at dressing changes, as well as topical antiseptic intervention. Use of antibiotics to treat infections in chronic wounds requires strict antibiotic stewardship.