A vial adaptor assembly , suitable for use with a vial containing a medicament and a syringe adaptor , which is in turn connectable to a syringe having a piston adapted for selectable displacement in a first direction for drawing fluid into said syringe and in a second direction for expelling fluid from said syringe , said vial adaptor assembly comprising: a vial connector for non-removable connection with said vial containing a medicament; a syringe adaptor connector for connection with said syringe adaptor ; a pressure equalization chamber having a variable volume, which is sealed from the outside environment during use; a liquid pathway communicating between an interior of said vial containing said medicament and an interior of said syringe when said syringe adaptor is connected to said syringe adaptor connector and said syringe is connected to said syringe adaptor and said vial connector is connected to said vial containing said medicament; and a venting pathway communicating between said interior of said vial containing said medicament and an interior of said pressure equalization chamber , when said vial connector is connected to said vial containing said medicament, characterized in that said pressure equalization chamber and said venting pathway are mutually configured such that, when said syringe adaptor is connected to said syringe adaptor connector and said syringe is connected to said syringe adaptor and said vial connector is connected to said vial containing said medicament, substantially all of any of said medicament that becomes located within said pressure equalization chamber is removed therefrom via said venting pathway and returned to said interior of said vial by displacement of said piston of said syringe in said first direction. a vial connector for non-removable connection with said vial containing a medicament; a syringe adaptor connector for connection with said syringe adaptor ; a pressure equalization chamber having a variable volume, which is sealed from the outside environment during use; a liquid pathway communicating between an interior of said vial containing said medicament and an interior of said syringe when said syringe adaptor is connected to said syringe adaptor connector and said syringe is connected to said syringe adaptor and said vial connector is connected to said vial containing said medicament; and a venting pathway communicating between said interior of said vial containing said medicament and an interior of said pressure equalization chamber , when said vial connector is connected to said vial containing said medicament, characterized in that said pressure equalization chamber and said venting pathway are mutually configured such that, when said syringe adaptor is connected to said syringe adaptor connector and said syringe is connected to said syringe adaptor and said vial connector is connected to said vial containing said medicament, substantially all of any of said medicament that becomes located within said pressure equalization chamber is removed therefrom via said venting pathway and returned to said interior of said vial by displacement of said piston of said syringe in said first direction. <EOS>