The feasibility of using sequential breast volume measurements as a method of studying short-term rates of milk synthesis in women has been established. We have developed a rapid Computerized Breast Measurement system for the determination of breast volume, based upon the Shape Measurement System. A circle encompassing all the breast tissue is drawn in black face paint on the subject's skin. Six patterns of sixty-four horizontal light stripes are projected onto the breast and chest wall surface. A CCD camera relays video images to a computer, which produces a model of the chest by active triangulation. The volume of the breast and the chest wall segment enclosed by the circle is then calculated. The precision of the method was dependent upon the subject repositioning carefully. The coefficient of variation of replicate measurements was 1.6%. The accuracy of the method was established by comparing the change in breast volume before and after a breast-feed with the amount of milk removed by the infant as determined by test weighing. There was a close relationship between the removal of milk by the infant (x) and the change in breast volume (y), (r = 0.93, n = 73, y = 1.10x - 3.25). The rates of milk synthesis between breast-feeds, for six women determined on one to eight occasions, varied from 11 to 58 ml/h. The results show that the amount of milk available in the breast is not necessarily an important determinant of the amount of milk removed by the infant at a breast-feed.