[en] In a number of cases it is necessary to estimate the radiation dose to organs far away from the target volume of a patient receiving radiotherapy, e.g. the dose to the gonads or to the fetus of a pregnant patient, often called the peripheral dose. For an accurate calculation of the peripheral dose due to brachytherapy, the tissue scatter and absorption as a function of distance r, T(r) needs to be taken into account. Historically, T(r) data from measurements and Monte Carlo calculations have been fitted to various algorithms (Meisberger, van Kleffens, and others). These calculational methods are, however, inappropriate in the range of distances above 10 cm. In the present work, results of measurements and EGS calculations are reported to determine the dose at distances up to 60 cm from Cs-137, Ir-192 and Co-60 sources. The influence of the size of the phantom was investigated. Several mathematical models to fit the data were investigated. The model of Kornelsen and Young, T(r) = (1 + k_a.(μ.r)^kb).exp(-μ.r), proved to give the best fit to the results. Parameters for this model were derived for the three isotopes. The total reference air kerma (TRAK), which is the sum of the products of the reference air kerma rate of the sources of an implant and the duration of the application, can then be used: with a simple application of the inverse square law, neglecting effects from patient size and tissue inhomogeneities, a good approximation of the dose-in-patient in the range 10 cm < r < 60 cm is obtained from: D(r) = TRAK ^* (100/r)^2* T(r). A few experiments in a Rando Alderson phantom are presented to support the measurements and the calculations