A rack or holder for test tubes and the like comprising a base and at least one test tube support plate member spaced apart from the base substantially parallel thereto and provided with a plurality of regularly arrayed apertures for placement therethrough of the test tubes. The base is provided with apertures each vertically aligned with a corresponding aperture in the support plate members. The apertures in the base or, alternatively, the apertures in the support plate member are each provided with a circular groove in which is disposed a toroidal resilient member, such as an O-ring or the like, having an internal diameter slightly less than the outside diameter of the test tubes. A test tube is normally supported in the rack by being introduced through the aligned apertures of the support plate member and of the base and pushed through the toroidal resilient member. The toroidal resilient member resiliently and frictionally engages the periphery of the test tube and holds it securely in position in the rack. Alternatively, by placing toroidal resilient members in grooves in the apertures in the support plate member, or plate members in arrangement wherein several spaced apart superimposed plate members are used, and by pushing the test tubes only part of the way through the support plate member, there is provided a visual indication of the status of an operation or chemical reaction being effected in the diverse test tubes as a function of the vertical positioning of the test tubes in the rack.