An apparatus for fractionation and infusion of radiopharmaceuticals, comprising: a fractionation unit for fractionating into a number of calibrated doses an amount of radioactive liquid contained in a multidose vial; one or more devices for administration thereof to a number of patients, and means for transferring in succession said doses from the fractionation unit to said one or more devices for administration thereof to a number of patients; and connections (21, 23, 25) for setting said fractionation unit in communication with said one or more administering devices for transfer of the doses to the individual patients, said apparatus being characterized in that it comprises a controlled-atmosphere chamber containing means (10, 12, 24) for connecting said connections (21, 23, 25) to a line for connection to said administering device, said means (10, 12, 24) comprising mobile connectors (10, 12), wherein said mobile connectors (10, 12) comprise: a first mobile arm carrying a connection to a line for transfer of the liquid to said administering device; and a second mobile arm provided with at least two seats for housing the connection to an input line and the connection to an infusion set provided for the patient and/or a plug, wherein said second arm is mobile for bringing at least two of said seats alternatively into a position for connection with said line, and said first mobile arm is mobile for displacing said connection to the administration line between a position of connection close to said seats and a detached position of separation. a fractionation unit for fractionating into a number of calibrated doses an amount of radioactive liquid contained in a multidose vial; one or more devices for administration thereof to a number of patients, and means for transferring in succession said doses from the fractionation unit to said one or more devices for administration thereof to a number of patients; and connections (21, 23, 25) for setting said fractionation unit in communication with said one or more administering devices for transfer of the doses to the individual patients, said apparatus being characterized in that it comprises a controlled-atmosphere chamber containing means (10, 12, 24) for connecting said connections (21, 23, 25) to a line for connection to said administering device, said means (10, 12, 24) comprising mobile connectors (10, 12), wherein said mobile connectors (10, 12) comprise: a first mobile arm carrying a connection to a line for transfer of the liquid to said administering device; and a second mobile arm provided with at least two seats for housing the connection to an input line and the connection to an infusion set provided for the patient and/or a plug, wherein said second arm is mobile for bringing at least two of said seats alternatively into a position for connection with said line, and said first mobile arm is mobile for displacing said connection to the administration line between a position of connection close to said seats and a detached position of separation. a first mobile arm carrying a connection to a line for transfer of the liquid to said administering device; and a second mobile arm provided with at least two seats for housing the connection to an input line and the connection to an infusion set provided for the patient and/or a plug, wherein said second arm is mobile for bringing at least two of said seats alternatively into a position for connection with said line, and said first mobile arm is mobile for displacing said connection to the administration line between a position of connection close to said seats and a detached position of separation.