A microcatheter for delivery of embolic fluids includes an outer memberdimensioned for insertion within a blood vessel adjacent an embolization site.The outermember defines a first longitudinal lumen, and an inner member is selectivelypositionable within the first longitudinal lumen of the outer member. Theinner memberdefines a second longitudinal lumen and has a delivery port in fluidcommunication withthe second longitudinal lumen for passage and delivery of embolic fluidstoward theembolization site. A valve is disposed within the outer member. The valve isdimensioned to establish a substantial seal about the inner member, tominimize entry ofthe embolic fluids within the first longitudinal lumen of the outer membersubsequent todelivery thereof toward the embolization site.
