The particulate loading in the process streams of coal conversion and gasification plants must be accurately determined for reasons of environmental health and safety and the protection of operating equipment such as gas turbines. A common method of obtaining these measurements is with aspiration probes. Deposition of particulate on the probe walls is a source of significant error in these measurements. This report reviews previous literature on deposition in sampling tubes for laminar and turbulent flows, the effects of the entrance region and bends in the sampling lines. A research plan is proposed for additional work in the analysis of deposition. Experimental work is also proposed to verify the analytical studies. The objectives of the research program are to develop methods to correct for the effects of deposition in sampling lines.