[en] The intensities of γ-rays emitted following the β⁺ decays of ³⁹Ca and ³⁵Ar were measured by using a Ge(Li) detector to detect the delayed radiation from a KCl target bombarded by 13-MeV protons. From these results the experimental log(ft) values and related B(GT) values for the ³⁵Ar and ³⁹Ca decays are deduced. These are compared with shell-model calculations together with a recent computation by Towner and Khanna of the higher-order corrections due to configuration-mixing outside the sd shell, isobar currents and other meson-exchange currents. We concentrate on the significance of the l-forbidden 1d/sub 3/2/ - 2s/sub 1/2/ Gamow-Teller transition in mass 39 and comment on its relation to the corresponding M1 transitions in ³⁹Ca and ³⁹K. 38 references