During 1991, large and distinctive Forbush decreases in cosmic-ray intensity were observed at Pioneer 11 at 34 AU on 21 August and at Pioneer 10 at 53 AU on 30 September. An apparently related shock passed Voyager 1 at 46 AU on 14 September. These three events are plausibly associated with each other and with a large Forbush decrease at the Earth on 12 June. The apparent radial speed of propagation was about 820 km s-1, independent of radial distance; and the decrease of cosmic-ray intensity was of similar magnitude (≈20 percent) at Earth, Pioneer 11, and Pioneer 10, i.e., over a radial range 1 to 53 AU and over a range of heliocentric ecliptic longitude at least as great as 173¿. For over a month following passage of the interplanetary shock by Pioneer 11, detectable intensities of locally accelerated protons of Ep≈1 MeV were present. The causative solar flare for the entire family of apparently related events was identified with reasonable certainty as a 3B/X 12.0 one in active region 6659 on 11 June at W17 N31. These new observations together with comparable ones reported previously provide the basis for a new quantitative model of the propagation of Forbush decreases in the outer heliosphere, described by RWF in a paper submitted to the Journal of Geophysical Research. ¿ American Geophysical Union 1992