A method for contamination-free transfer of liquid from one container to another, and devices to carry out the method are disclosed. Contamination-free transfer means that during the transfer process there is no (1) leakage of (a) the liquid, (b) air contaminated by the liquid, and (c) vapor from the liquid to the surroundings, and (2) surrounding contaminants from outside the containers that contact the liquid. The method's advantages include its simplicity, and the contamination-free transfer as defined above. The devices are adapted to effect contamination-free transfer of a hazardous drug to and from any container equipped with a standard connector port.