The crystal structure and ionic conductivity of the Ag+-rich phases in (AgI)(x)-(PbI2)(1-x) have been investigated by powder neutron diffraction and impedance spectroscopy studies of samples with x=2/3 and x=4/5. The phase diagram in this region appears to be somewhat simpler than that presented previously with a single phase stable at T greater than or equal to 420 K (x=2/3) and T greater than or equal to 400 K (x=4/5). This is a superionic phase, with sigma similar to 0.1 Omega(-1) cm(-1) at T=420 K, in which the anions form a face centred cubic (f. c. c.) sublattice of lattice parameter a similar to 6.34 Angstrom. We therefore label this phase as f.c.c. -AgxPb1-xI2-x. The structure adopts the centrosymmetric space group Fm (3) over barm, with the majority of cations (over 90%) located in the octahedral 4(b) cavities and the remainder within the tetrahedral 8(c) interstices. Whilst this sixfold co-ordination to I- is to be expected for Pb2+, it is relatively unusual for Ag+, especially within a superionic phase. To highlight this behaviour, comparison is made with the f c. c.-structured superionic phase alpha-Ag2HgI4. On cooling, the f.c.c.-AgxPb1-xI2-x phase with x=4/5 dissociates at T approximate to 400 K to form AgI and PbI2. The former adopts its zinc blende-structured gamma phase whilst, unusually, the latter is stabilised in its 6R polytype rather than the normal 2H modification. The gamma-AgI+6R-PbI2 mixture appears to be stable at ambient temperature indefinitely. For the x=2/3 case, 6R-PbI2 appears separately on cooling at approximate to. 420 K and, on further cooling, complete dissociation to form a two-phase mixture of gamma-AgI and 6R-PbI2 occurs by approximate to 390 K.