A catheter according to the present invention includes a multiple lumen catheter for delivery of a liquid embolic composition through a first lumen and delivery of a solidification agent through a second lumen. The catheter allows adjustment of the relative longitudinal position of the two lumens to control the solidification of the embolic composition within a blood vessel. The multiple lumen catheter system is used by inserting the catheter endovascularly into an aneurysm site and injecting a liquid embolic composition through the first lumen while injecting a solidification agent through the second lumen to wash the area of the aneurysm of blood which has become saturated with solvent, while replacing it with a fresh solidification agent. The controlled solidification of the liquid embolic composition by use of the solidification agent allows the aneurysm to be filled precisely and rapidly even when the aneurysm is located such that gravity does not cause the liquid embolic composition to flow into the aneurysm.