The spin-modulated noise from the dipole connected to the sounder receiver on the Isis 1 spacecraft has been used along with the computation of ray paths to deduce the direction of propagation of auroral kilometric radiation (AKR). On the basis of three passes with fixed-frequency measurements at 0.48 MHz it is concluded that in the generation region at about 3500-km altitude the wave vectors make an angle between about 60 ¿ and 90 ¿ with respect to the local magnetic field. That is, they are predominantly downcoming. Also, in using the sounder records the plasma frequency FN≲50 kHz, FH in the generation region (FN≲50 kHz, FH?450 kHz). When these Isis observations are combined with previous evidence on AKR, from which it was concluded that it propagates predominantly in the right-hand polarized X mode, serious disagreement with a number of theories, particularly those that predict the left-hand-polarized O mode, results. However, two theories of a quite different nature, direct cyclotron radiation and a three-wave interaction involving an ELF/VLF wave, give some prospect of accommodating all the observations.