The Department of Energy is sponsoring a multiphase program to investigate the filtration potential of the moving bed granular filter (GBF) for application in pressurized high temperature energy conversion systems. Phase I included the development of a mathematical model, a cold flow parametric test series in a 0.746 Nm/sup 3//s GBF, and investigations of potential dust plugging problems at the inlet screen. During the experimental program, collection efficiencies of 99% and filter outlet loadings less that 0.0074 g/m/sup 3/ were demonstrated. The objectives of Phase II are to investigate the effects of elevated temperature and coal combustion particulate on GBF filtration performance, to update the analytical model developed in Phase I to reflect high-temperature effects, to optimize filter internal configuration, to demonstrate long duration GBF performance relative to corrosion, deposition, erosion, filtration efficiency, reliability, controllability, and to design and construct a 0.879 Nm/sup 3//s, 660 kPa filter for delivery to DOE. Hot flow testing to date has confirmed that the GBF configured with inlet and outlet screens has exhibited a tendency for extensive and irreversible ash plugging. As an alternative, the potential advantages produced by a screenless configuration, having higher filtration efficiency, has been achieved during both cold flow and hot flow tests as previously reported. Feed and solid compositions from test P704, the 400-hour GBF test, are presented. A status report on the design of the high pressure GBF along with operation details for purging the GBF of corrosive gases upon shutdown and granular reserve sensing during its operation are detailed.