The neutron scattering by isolated clusters of Mn2+ions in a single‐crystal specimen of KMn0.18Zn0.82F3has been studied as a function of wave‐vector transfer Q at 4.3 K and as a function of temperatureTat Q=2&pgr;a−1(0.55,0.55,0.55). At lowTwe observe peaks corresponding to the ground‐state transitions of isolated pairs and triplets and to two excited‐state transitions of pairs. The frequencies &ugr; of these peaks lead directly to accurate values for the exchange interactionJ, e.g., 0.100±0.004 THz and 0.098±0.002 THz from the ground‐state transitions of pairs (&ugr;=2J) and triplets (&ugr;=7J) respectively. Exact calculations of the neutron scattering by isolated pairs, triplets and quartets of Mn2+ions interacting via nearest‐neighbor antiferromagnetic exchange give a reasonably good description of the principal features of the measurements. There are, however, discrepancies that are probably attributable to the scattering by larger clusters.