The present invention is directed to a device for a portable convection enhanced delivery system that allows administering liquids to specific locations within the body, especially tissues and tumors also allowing outsubject treatment. The application system comprises a portable extracorporal pump with a fluid reservoir that is connected via an infusion system to an infusion catheter placeable to any tissue or tumor the fluid should be administered to by high flow microperfusion. The system enables administration of fluids of any kind by convection enhanced delivery also in out-patient treatment. The system can be used for delivering various drugs, proteins, protein toxins, antibodies-for treatment or imaging, proteins in enzyme replacement therapy, growth factors and viruses or oligonucleotides in gene therapy etc. The application methods as well as the surgical method to implant this device are enclosed to this invention.