Abstract: A shaker apparatus is provided for laboratory testing. The apparatus comprises a base that is reciprocally movable relative to a sub-base. A frame is mounted to the base and includes spaced apart vertical supports with a horizontal support assembly rotatably mounted therebetween. A plurality of test vessels are mounted to the horizontal support assembly and can be rotated with the horizontal support assembly 180.degree. relative to the base. The vessels may be subjected to simultaneous shaking for identical periods of time. The horizontal frame assembly to which the vessels are mounted can be inverted between adjacent periods of shaking to permit selected refilling of the vessels, escape of gases therefrom and drainage of material from the vessels.