Measurement of heart-girth (chest circumference) is commonly used to estimate dairy heifer body weight from previously derived equations or tables. In this experiment, variability of heart-girth measurements as they are taken in the field was analyzed to determine the standard deviation within a group of 26 Holstein heifers of various ages weighing 42–590 kg. Standard deviations were 2.19 cm among 26 observers and 2.74 cm within any one observer.