This study tries to determine if yellow bone color is a predictor of tetracycline levels in bone or other tissue.To test this 30 pigs were given tetracycline for different lengths of time and by different ways of administration. The different treatments were: Group 1 -chlortetracycline in the feed at 660 ppm for 12 weeks. Group 2 – chlortetracycline in the feed at 660 ppm for 3 weeks. Group 3 – chlortetracycline in the feed at 110 ppm for 12 weeks. Group 4 – chlortetracycline in the feed at 110 ppm for 3 weeks. Group 5 – 1 g tetracycline per 8 L water for 5 days. Group 6 – 300 mg per 45 kg body weight of oxytetracycline for 3 days. When the pigs were processed the bones were assessed to see if they changed color and for UV fluorescence. Some bones were also collected and ground to a powder and then tested for levels of tetracycline. The results show that three types of tetracycline used in the study were distinguishable. Pigs receiving 660 ppm of chlortetracycline for 3 weeks in feed during the early grower stage ranged from 12 to 23 ppm. Levels found in discolored bones at slaughter were similar, averaging 23 ppm of chlortetracycline. This study suggests that exposure to relatively low levels for relatively short periods of time resulted in tetracycline levels present in bone at slaughter that were similar to the levels found in pigs identified with bone discolouration. Levels in other organs such as liver, kidney, and muscles were below detectable limits.