Abstract: A push-to-connect fitting for sealed connection to a synthetic resin tube end. The fitting includes a body, an eyelet, a nut threadedly connected to the body, and a radially constrictible sleeve for retaining the tube end effectively positively within the fitting. The fitting is arranged to be connected to the tube end by a coaxial insertion of the tube end into the fitting with the tube end being received between the sleeve and the eyelet in moving to the fully inserted position. The sleeve is provided with annular gripping portions, one of which is slidably engaged by the tube end as it is inserted into the fitting. The one tube portion is arranged to be mechanically interlocked with the tube end as a result of an outward movement of the tube end from the fully inserted position whereupon the sleeve is concurrently urged axially outwardly with the tube end.