Abstract: A photomultiplier tube in which the anode, which is positioned adjacent to the last dynode, is not supported by the side supports which support the dynodes as was done in the prior art, but is supported by the stem. Thus, the anode "floats" with respect to the side supports and with respect to the dynodes which are rigidly attached to the side support. An advantage of this structure is improved electrical properties, e.g., a reduction in dark current, improved signal to noise ratio and reduction in hysteresis. The floating anode is particularly applicable to box and grid type of dynode structures used in small diameter, e.g., one-half and three-fourth inch tubes.