In the formula for calculation of radiation dose from a radionuclide deposited internally, as originally presented by Marinelli, Quimby, and Hine (1), a factor g appears. This is designated as the geometrical factor, and for any point of reference represents the integration of e-μr.r/r2 over the pertinent volume. Here r is the variable distance from all points in the volume to the point in question, and γ, is the appropriate absorption coefficient. In the reference quoted this factor is evaluated for the center of a sphere, up to a radius of 10 cm, and for the midpoint of the axis of cylinders. The doses at these points would be maximum for the particular figure. Tables for these central g values were first published in 1951 (2). If an average dose throughout the figures is desired, g must be obtained for an “average” point. For example, in the case of a sphere, g at the center = 41πR, and on the surface is 21πR, so an average g (g̅), might be expected to be 31πR, and in fact this can be proved to be true. For the cylinder the procedure is not simple, but in fact demands a rather complex analytical approach. In 1956 (3) a table appeared which purported to be the average g (g̅) values for cylinders. Details for its production were not given, but since no other values were available, it was accepted and widely copied into other books (4, 5). Within the past year, however, it began to appear that these values were too small. After some checking it became evident that they referred not to an average, but to a point on the surface of the cylinder at the end of the axis. Hence they would be appreciably less than the average, and all doses calculated from them would come closer to being minimum than average values. It is, of course, a question as to what dose is desired in such a calculation—maximum, minimum, or average. The general feeling seems to be for an average. In any case it is desirable that the term “average” be removed from these published values, that they be properly labeled, and that tables for g̅ values be made available. In 1949, Bush (6) published a general method for calculating the integral dose received from a uniformly distributed radioactive isotope, but included no tabular data except for patients carrying a specified radium content. This table has been adapted to provide the currently used g factors for the human body (3, 5). In order to provide a comparable table for g̅ factors for cylinders the method outlined by Bush (6) was employed. The results for the average g, that is g̅, for cylinders, using an effective absorption coefficient of μ, = 0.028, are given in Table 1.