Abstract: Remote controlled afterloader apparatus and method positions high activity radioactive sources through a catheter within a human body for treatment of cancerous tissue. The afterloader including an operating console and a remotely located wire driver. The wire driver includes active and dummy source wires and channels for the storage of such wires. Stepper motors precisely position the wires in response to computer control and data from wire position encoders. An emergency dc motor retraction system is provided for the active wire. A non-computerized cross-check interlock and emergency retraction system provides a high degree of safety against system malfunction. A turret is provided with safety locking and cross-checking systems to permit use of multiple catheters. The dummy wire is inserted into each catheter to verify catheter integrity prior to insertion of the active wire.