Methods and apparatus for maintaining urinary continence in normally incontinent individuals. The present invention involves the non-surgical implantation of a bolus of ferromagnetic material into the bladder. The bolus of ferromagnetic material may comprise a biocompatible membrane, containing a ferromagnetic material. The bolus will normally rest at the juncture between the bladder and the urethra and will prevent the flow of urine from the bladder into the urethra. Essentially, the bolus serves as a seal between the urethra and the bladder. When it is desired to void the bladder, the ferromagnetic bolus is moved out of the intersection between the bladder and the urethra by positioning a magnet along the external surface of the person's body and manipulating the magnet until the desired movement of the bolus is accomplished. Movement of the magnet is sufficient to displace the bolus such that flow may be initiated from the bladder into the urethra.