Abstract: A composite medicament container including a vial to contain a dry powdered medicament, an outlet opening in the vial, a Lyo-stopper closing and sealing the outlet opening, and a flexible liquid container to contain a diluent for the dry medicament. The liquid container has a discharge port having an ellipsoidal shape. There is a closure plug in the discharge port. The closure plug has an ellipsoidal configuration and a size to mate with the interior of the discharge port and be secured therein. The configurations and sizes of the discharge port and said closure plug co-act to provide an enlarged, closely contacting extensive scaling area. The vial opening has a circular external configuration so that the vial outlet opening and the liquid container closure plug are mateable. Also included is a composite interengaging and sealing means which is operatively attaching and sealing the containers in mated relationship for intermixing the materials therein.