This work was inspired by a recent case of child abuse where the question of the age of the bruises on the body was raised. The first part of this paper reviews published work on bruises. It illustrates the paucity of work in this field and the absence of studies of the colour changes in bruises of human skin with time. The second part of this paper consists of our own study of the appearance of bruises. The aim was to identify the colour changes which occur in bruises and over what time-scale, in order to determine whether bruises can be aged by appearance. A total of 369 photographs were obtained of bruises aged less than 6 h and up to 21 days old, in 89 subjects aged 10-100 years. It was found that the development of a yellow colour was the most significant change (subjects aged less than 65, P less than 0.001; subjects aged greater than or equal to 65 years, P less than 0.001). The development of a yellow colour occurred significantly faster in subjects aged less than 65 years. (P less than 0.001). The appearance of a blue and purple/black colour was of lesser significance. The appearance of a red colour did not alter significantly with time. From this study it was only possible to conclude that a bruise with a yellow colour was more than 18 h old.