This report reviews individual-related variables (age, sex, race, anatomical site, skin surface properties), intra- and interindividual variation (temporal, physical and mental activity, orthostatic effect, menstrual cycle/menopause), environment-related variables (light conditions, temperature) and various instrument-related variables that influence skin colour. CIE colorimetry (Minolta Chroma Meter) and spectrophotometric measurement (Derma Spectrometer) are considered. The guidelines give recommendations for measuring conditions and procedures.