Corrosion which is tolerable from the standpoint of system mechanical integrity may cause substantial problems if the corrosion product is released and deposited at locations where it interferes with heat transfer or coolant flow. Furthermore, neutrons from the fusion reaction activate the corrosion product, causing radiation fields in maintenance areas near piping and components where the activated material is deposited. Preliminary estimates suggest that formidable problems may occur in a lithium-cooled stainless-steel primary circuit due to corrosion product deposition. If the estimated order of magnitude is confirmed in future studies, new concepts in corrosion control or corrosion product removal would need to be developed for lithium-cooled stainless-steel Controlled Thermonuclear Reactor (CTR) systems. Other fusion reactor system concepts and materials appear to offer alternatives which tend to minimize corrosion product transport.