The synthesis of individual carbon nanotubes (CNTs) with controlled diameters at lithographically predefined locations has been achieved. Employing conventional catalyst-mediated chemical vapor deposition (CVD), isolated CNTs were grown out of nanoholes in silicon dioxide created by optical lithography. This allows the precise placement of individual CNTs on substrates. Furthermore, the diameter of each CNT adjusts to the hole size, which makes it possible to control this important property separately for individual CNTs. This approach is a step toward the parallel manufacture of nanotube-based devices in a scalable batch process. In particular, the integration of CNTs into conventional silicon-technology with potential applications as interconnects, transistors, and memory cells becomes possible.