Milk production performance is one of the major economic traits for the selection programme in the dairy cattle.The reliable information on production, pedegree and progeny records for most of the cattle particularly in village conditions are not available. Therefore at the time of selection for individual superiority, it need to depend on body confirmation, external features, structure of udder, milk vein, milk well etc, because average confirmation of cows does indicate a suitability of milk production. For this reason the animal breeders have tried to establish a close relationship between the external characteristics and milk production. With this in view the present study was made with the objective to determine length, thickness of milk vein and diameter of milk well in H.F. crossbred cows, to determine correlation coefficient between the size of milk vein and milk well with milk yield in four subsequent lactations of H.F. crossbred animals. The information furnished in this book is useful for livestock breeders, teachers, post graduate students and farmers in selection of dairy animals.