The use of small silver-activated phosphate glass rods for ionizing radiation dosimetry is described. Convenient methods for the handling, reading, and calibration of the rods are reported. With the apparatus described fluorescence of the rods may be determined with a precision of 4 per cent. With 20 MeV electrons and the gamma-rays from radium, iridium-192, and cobalt-60, the smallest detectable absorbed dose is approximately 30 rads. With 250 and 180 kVp X-rays the smallest detectable dose is 3 rads. Variation in sensitivity of the rods with depth in an absorbing medium such as water is small with 22 MeV electrons, 250 kVp X-rays and 180 kVp X-rays incident on the surface. With the gamma-rays from cobalt-60 a 40 per cent change in sensitivity was observed. The effects of exposure temperature, storage time, and ultraviolet exposure on the fluorescence of the rods are reported as well as the results of a limited number of applications.