A hemostasis valve may be used with a catheter such as an aspiration catheter. The hemostasis valve comprises a support, and at least a first lever, pivotably carried with respect to the support. A collapsible tubular sidewall defining a valve lumen is carried by the support. A filament is formed into a loop around the tubular sidewall, the filament having at least a first tail portion extending away from the loop to the first lever. A first spring may be configured to move the first lever in a direction that pulls the first tail portion away from the tubular sidewall, reducing the diameter of the valve lumen in response to reducing the diameter of the loop. A second tail portion may extend away from the loop to a second lever. Each tail portion may be attached to its respective lever, or may be slidably advanceable around a fulcrum on the lever and attached with respect to the support.

A valve body and a medical instrument provided with the valve body can stably maintain sealing performance for preventing air/blood leakage while maintaining a smooth insertion feeling even when various types of medical devices are repeatedly inserted and removed. The valve body includes a main body portion having oppositely facing first and second surfaces, an outer peripheral surface extending between the first and second surfaces, and an insertion portion having an inner surface defining a gap that allows insertion of a medical device and formed at least on the first surface. The main body portion contains a self-repairing material that allows self-repairing damage resulting from contact with the medical device. At least part of the inner surface of the insertion portion is provided with a coating layer that prevents the gap from being closed by self-repair when portions of the inner surface of the insertion portion contact each other.