Very large amplitude fluctuations in electron density, temperature, and flow velocity were a prominent aspect of the solar wind interaction with comet Giacobini‐Zinner during the ICE encounter in September 1985. These fluctuations were detected at a distance of at least 9 × 105km and grew in amplitude as ICE approached the comet, peaking in amplitude 6 × 104km from closest approach. A typical period associated with the fluctuations was ∼2 min, which corresponds to a scale length in the solar wind frame of ∼5 × 104km. For the most part these fluctuations appear to be a product of one or more plasma instabilities associated with the solar wind pick up of comet