This is a catheter device for delivering vaso-occlusive materials or devices to a desired site with the body. The catheter is a single lumen valved balloon catheter that enhances the accurate placement of the vaso-occlusive material or device. The balloon may be positioned such that it blocks the opening to a vascular malformation such as an aneurysm. In one embodiment, the balloon is automatically inflated as the vaso-occlusive material or device engages a constrictive feature near the distal end as the device is discharged. The catheter device may also have a lengthened distal section that may be placed within the malformation or aneurysm to improving the filling capability of the device. The catheter device may be constructed to have a number of advantageous radioopaque markers to aid in accurately discharging the vaso-occlusive material or device.