A dairy cow body condition scoring system was devised by the author as a practical means of determining the body condition, or fitness pertaining to the degree of body fat of dairy cows at any point during the lactation cycle. The factors considered were the thoracic and lumbar regions of the vertebral column (chine, loin and rump), spinous processes (loin), anterior coccygeal vertebrae (tailhead), tuber sacrale (hooks), and tuber ishii (pin bones). All factors in the body condition scoring system must be considered while appraising each cow. Each cow was scored on a 1 to 5 scale with 1 indicating severe undercondition and 5 indicating severe overcondition. During an 18-month period, 28 cows in each of 29 Virginia dairy herds were used for obtaining body condition scores, body weight, frame size measurements and blood samples. Herds were chosen according to rolling herd milk production average and cows were chosen at random from within five Estimated Relative Producing Ability groupings to insure a representative sample of herds across and levels of production in Virginia and of cows within each herd. Herds were sampled at 3-month intervals and complete Dairy Herd Improvement Association records were obtained for each cow in each herd. The relationships of dairy cow body weight, frame size measurements, milk production and related parameters, and blood profiles to the body condition scoring system were determined. Body condition using this method was found to be independent of frame size and only moderately correlated with body weight, the number of intercostal spaces and the ratio of body weight to wither height. Body condition was found to be relatively low during early lactation and to increase through late lactation and remain constant during the dry period. Dairy cows of greatest milk production efficiency did not increase significantly in body condition throughout lactation, had fewer days open, but had less persistency of lactation. Dairy cows that increase significantly in body condition throughout lactation were less efficient milk producers, had a greater number of days open, had relatively high body condition scores in late lactation, but had greater persistency of lactation. Blood parameters, although statistically significant in many cases, were found to be of little or no practical value when compared between body condition, stage of lactation, and dairy merit groupings. The dairy cow body condition scoring system is a practical means of quantitating body condition of dairy cows. / Ph. D.