Muscle colour has been recorded on pigs tested at the national pig progeny testing stations in Great Britain since 1958. From September 1960 a muscle colour score on a scale of 1 to 7 points has been given by comparing the muscle colour with a series of seven coloured discs of increasing colour intensity. These discs were prepared specifically (by Tintometer Ltd. Of Great Britain) to score muscle colour in pigs. The higher the colour score the more desirable the colour was adjudged to be by the testing station personnel. However, scores of 6 and 7 were very infrequent and no assessment of their desirability was made. Carcasses were cut at the last rib on the day after slaughter at about 200 lb. live-weight and muscle colour was scored on the cut surface of the longissimus dorsi muscle (eye muscle).