The three-dimensional electron spectrometer of the R¿me plasma analyzer-complete positive ion, electron and ram negative ion measurements near comet Halley (RPA-COPERNIC) experiment aboard the Giotto spacecraft, although damaged during the comet Halley encounter in March 1986, has provided very new results during the encounter on July 10, 1992, with the weakly active comet Grigg-Skjellerup (G-S). The main characteristic features of the highly structured interaction region extending from ~26,500 km inbound to ~37,200 km outbound are: (1) a broad inbound ''bow wave transition'', (2) a cometosheath characterized by strong oscillations of the electron fluxes with peak-to-valley ratios up to 20:1; the levels of oscillations are much larger and generally more coherent than at comet Halley or at comet Giacobini-Zinner, despite the much lower neutral gas production rate, (3) a ''mystery'' region, identified by significant fluxes of hundreds of eV electrons, and a ''mysterious'' transition, about halfway between the bow wave transition/bow shock regions; they are observed as for comet Halley, confirming their large importance in the solar wind-comet interaction at 1 AU, (4) an inner region which coincides with the magnetic pileup region; at closest approach, the cold cometary electron fluxes display a prominent maximum, and (5) a sharp outbound bow shock and its possibly associated electron foreshock. These results are compared to the results obtained by the same instrument during the Giotto comet Halley fly-by. Despite the large difference in the size of the interaction regions (~60,000 km for G-S, ~2000,000 km for Halley) due to 2 orders of magnitude difference in cometary neutral gas production rate, there are striking similarities in the solar wind interactions with the two comets. ¿ American Geophysical Union 1993