New optical methods of studying the infant brain have been developed over the last 20 years. These techniques make use of a window of transparency of biological tissue to near infrared light. Using spectrophotometry new insights have been gained into mechanisms of brain damage in newborn infants undergoing intensive care, and non-invasive functional activation studies have been pioneered in awake infants. Recently topographic mapping of activated cortex has become possible, and preliminary tomographic images of regional oxygenation in infants have been constructed. This is a rapidly changing field which offers exciting possibilities for studying both normal and abnormal child development.