Abstract: A device for aligning sample containers (particularly of the test tube type) regardless of the container's size, comprises a foot member provided with a tapered cavity for receiving the bottom end of the container, a holder for holding the other end of the container in a temporary position, and a head member having a tapered cavity for receiving the other or upper end of the container. The foot and head members are movable relative to one another so that the cavity of the head member can releasably engage the upper end of the container and align the container with a predetermined axis. The device can be used to mix and test sample fluids, as well as dispense and aspirate fluids into and out of the containers.