A fluid transfer assembly (100; 150; 160; 170; 180) for use with a first vial and a second vial for liquid drug reconstitution and administration purposes, the first vial having a vial opening and a vial stopper sealing the vial opening and a vial interior containing a liquid medicament, the second vial having a vial opening and a vial stopper sealing the vial opening and a vial interior containing a medicament under negative pressure, the liquid medicament intended to reconstitute the second vial's medicament to form reconstituted liquid drug contents, the fluid transfer assembly having a longitudinal axis and comprising: (a) a female vial adapter (110; 171; 181) having a top wall, a skirt with flex members for snap fitting onto the second vial, a pointed cannula for puncturing the second vial's vial stopper on snap fitting said female vial adapter on the second vial, said pointed cannula including a liquid transfer lumen for establishing flow communication with the second vial's vial interior, and a female connector in flow communication with said liquid transfer lumen; and (b) a male vial adapter (130; 172; 182) having a top wall, a skirt with flex members for snap fitting onto the first vial, a pointed cannula for puncturing the first vial's vial stopper on snap fitting said male vial adapter on the first vial, said pointed cannula including a liquid transfer lumen for establishing flow communication with the first vial's vial interior, and a male connector in flow communication with said liquid transfer lumen and for sealing said female connector on assembling said male vial adapter on said female vial adapter for reconstitution of the liquid drug contents, characterized in said female vial adapter having a venting arrangement (110A; 151; 161) including i) an air filter underlying said top wall, ii) at least one vent port formed in said top wall and iii) a venting lumen formed in said pointed cannula for establishing flow communication between said at least one vent port and the second vial's vial interior on snap fitting said female vial adapter on the second vial, and said male vial adapter having a sealing arrangement for sealing said at least one vent port during reconstitution of the liquid drug contents, the arrangement being such that pursuant to initial snap fitting of i) said male vial adapter on the first vial and thereafter ii) said female vial adapter on the second vial, the second vial's negative pressure draws the first vial's liquid medicament thereinto for reconstitution with its medicament for reconstituting the reconstituted liquid drug contents, subsequent axial displacement of said male vial adapter from said female vial adapter initially axially displaces said sealing arrangement from said at least one vent port to open said venting arrangement while said male connector continuously seals said female connector such that the second vial draws filtered air only thereinto to equalize its negative pressure and thereafter completes mechanical detachment of said male vial adapter from said female vial adapter for enabling administration of the reconstituted liquid drug contents. (a) a female vial adapter (110; 171; 181) having a top wall, a skirt with flex members for snap fitting onto the second vial, a pointed cannula for puncturing the second vial's vial stopper on snap fitting said female vial adapter on the second vial, said pointed cannula including a liquid transfer lumen for establishing flow communication with the second vial's vial interior, and a female connector in flow communication with said liquid transfer lumen; and (b) a male vial adapter (130; 172; 182) having a top wall, a skirt with flex members for snap fitting onto the first vial, a pointed cannula for puncturing the first vial's vial stopper on snap fitting said male vial adapter on the first vial, said pointed cannula including a liquid transfer lumen for establishing flow communication with the first vial's vial interior, and a male connector in flow communication with said liquid transfer lumen and for sealing said female connector on assembling said male vial adapter on said female vial adapter for reconstitution of the liquid drug contents, characterized in said female vial adapter having a venting arrangement (110A; 151; 161) including i) an air filter underlying said top wall, ii) at least one vent port formed in said top wall and iii) a venting lumen formed in said pointed cannula for establishing flow communication between said at least one vent port and the second vial's vial interior on snap fitting said female vial adapter on the second vial, and said male vial adapter having a sealing arrangement for sealing said at least one vent port during reconstitution of the liquid drug contents, the arrangement being such that pursuant to initial snap fitting of i) said male vial adapter on the first vial and thereafter ii) said female vial adapter on the second vial, the second vial's negative pressure draws the first vial's liquid medicament thereinto for reconstitution with its medicament for reconstituting the reconstituted liquid drug contents, subsequent axial displacement of said male vial adapter from said female vial adapter initially axially displaces said sealing arrangement from said at least one vent port to open said venting arrangement while said male connector continuously seals said female connector such that the second vial draws filtered air only thereinto to equalize its negative pressure and thereafter completes mechanical detachment of said male vial adapter from said female vial adapter for enabling administration of the reconstituted liquid drug contents.