The variation of the electrical resistance R of EuMo6S8 with temperature T and applied magnetic field H was determined at pressures P to 19 kbar. At ambient pressure, the results are in agreement with previous work on samples of similar quality, where it was determined that variations of the carrier concentration were responsible for the very strong dependence of R on T and H. At P=8.5 kbar, the magnetoresistance is determined by the freezing out of the Eu2+ spins as H increases. For P>13 kbar, EuMo6S8 exhibits bulk superconductivity, and we investigated the upper critical magnetic field Hc2(T). The analysis of these results shows that our EuMo6S8 samples are clean superconductors. We observe that Hc2 is strongly reduced by pressure, perhaps due to an increase of the carrier concentration with pressure. © 1988 Plenum Publishing Corporation.