Four experiments were carried out on chronic female schizophrenic patients in order to determine the differential effects of colour upon their behaviour. The three primary colours, red, blue and green, were used. The patients, who fell into Arieti's second or third stages of schizophrenia, had a mean age of 45 years (range 38-50), and a mean duration of hospitalization of 19 years (range 9-30). All experiments were carried out in a small side room painted white, the colour of which could be changed by the use of coloured lights hanging centrally from the ceiling. The colours used had a fixed intensity of 2 foot candles at a distance of 2 feet.