Deciding whether to treat a scar or leave it alone depends on accurate diagnosis of scar type and scar site, symptoms, severity, and stigma Each year in the developed world 100 million patients acquire scars, some of which cause considerable problems, as a result of 55 million elective operations and 25 million operations after trauma. 1 There are an estimated 11 million keloid scars and four million burn scars, 70% of which occur in children. 1 Global figures are unknown but doubtless much higher. People with abnormal skin scarring may face physical, aesthetic, psychological, and social consequences that may be associated with substantial emotional and financial costs. This article reviews the spectrum of abnormal scar types, a range of problems associated with scarring, and provides advice on assessment, treatment, and new therapeutic developments.