The properties of waves with frequencies below 3 Hz observed upstream of low Mach number (2–3) interplanetary shocks are discussed. High-frequency emissions (0.2–2 Hz in the spacecraft frame) are commonly detected immediately upstream (<2 RE) of the shocks, whereas lower frequency emissions (∼0.05 Hz) are found to extend upstream to much greater distances (typically 10 RE). Both emissions are right-hand circularly or elliptically polarized and generally propagate within a 15° cone angle relative to the ambient magnetic field. The lack of a significant compressional component for either of these waves is in agreement with propagation parallel to the ambient magnetic field. Upstream waves are detected principally in association with quasi-parallel shocks (θBn < 65°). Assuming the waves are propagating outward from the shock, an expression is derived for the wave frequency in the solar wind rest frame. The waves are found to have rest frame frequencies of 0.05–1 Hz and 10−3 to 10−2 Hz. Arguments are presented which exclude the possibility that the high-frequency waves are standing whistler mode waves. The most likely source of these emissions is generation at the shock by 100 eV to 1 keV electrons and propagation of the whistler mode waves into the upstream region. The lower frequency 10−3 to 10−2 Hz waves propagate at speeds near the Alfvén velocity, and hence cannot outrun the super-Alfvénic shocks. These waves must be locally generated by plasma instabilities in the upstream region. Generation by Landau electrons or ions can be ruled out due to the observation of parallel propagation of the waves. The most likely source is 1–10 keV cyclotron-resonant ions propagating away from the shock. The upstream waves bear many similarities to those observed in the earth's foreshock. The frequencies, polarization, and typical upstream extent are nearly identical. It is also deduced that the lower frequency waves of both regions are generated by keV ions streaming away from the shock. There are some differences, however. Waves upstream of interplanetary shocks are found to propagate parallel to the magnetic field (<15°), are noncompressive (ΔB/B ≤ 0.25) and are generally lower in amplitude. Additionally, there are extraordinary interplanetary events, for which the scale of the upstream wave region is greatly extended (∼1300 RE or 0.04 AU) and the field takes on a more turbulent character. The latter events should be of interest in modeling Fermi acceleration of ions at collisionless shocks.