Abstract: A blood agitating and weighing device includes a base member and a support member, pivotally mounted with respect to the base member, for journally supporting a container, such as a flexible blood storage bag. A spring member is provided for biasing the support member to a first tilted position relative to the base member and a flexible bladder is positioned beneath the support member. The bladder is expandable in response to the introduction of pneumatic pressure therein to overcome the bias of the spring member to move the support member to a second tilted position relative to the base member. The bladder is contracted in response to the release of pneumatic pressure to allow the spring member to move the support member back to the first position. The support member is therefore alternately moved between the first and second positions by the alternating expansion and contraction of the bladder to agitate the blood in the container.