the Giotto spacecraft encountered a second comet, namely, P/Grigg-Skjellerup. Despite the small production rate of this comet (approximately 2 orders of magnitude smaller than that of P/Halley and 1 order of magnitude smaller than that of P/Giacobini-Zinner) the plasma flow showed several distinct flow transitions. We have applied theoretical models, previously developed to explain the existence and location of the flow boundaries at comets P/Giacobini-Zinner and P/Halley to this new data set for comet P/Grigg-Skjellerup. The observed bow shock crossings are used to evaluate the production rate of the cometary neutrals. Using this production rate, the position of the collisionopause and the ionopause are estimated. The observed location of the magnetic pile-up boundary corresponds well to the theoretical calculations. We also find the reason that a magnetic field-free region was not encountered was because the ionopause, while being sharp, was inside the spacecraft trajectory which had an estimated closest approach distance greater than 120 km. Finally we have used the observed spatial profile of the solar wind magnetic field together with a simple one-dimensional, multispecies chemical model to calculate the radial density profiles of the H20 group ions outside the bow shock. Comparison of the calculated total H20 group ion density profile with observations indicates a good fit in the inner region where the H20 + ion dominates. While the corresponding fit in the outer region, where the O + ion dominates, becomes progressively less satisfactory with increasing cometocentric distance, it is noted that the observations themselves are believed to be less reliable at these large distances. 1. 21,008 FLAMMER AND MENDIS: CONTAMINATED SOLAR WIND FLOW AT COMET GRIGG-SKJELLERU? Jones, and G. L. Sisoe, Comet-solar wind interactions: Dynamical length scales and models, Geophys. Res. Lett., 13,239, 1986. Mendis, D. A., et al., On the global interaction of the solar wind interaction with comet Halley, Ann. Geophys., 7, 99, 1989. Neubauer, F. M., et al., Preliminary results from the Giotto magnetometer experiment during the P/Grigg-Skjellerup encounter, Astron. Astrophys., in press, 1993. Schmidt, H. U., and R. Wegmann, Plasma flow and magnetic fields in comets, in Comets, edited by L. L. Wilkening, p. 538, University of Arizona Press, Tucson, 1982.