The current-carrying capacity and reliability studies of multiwalled carbon nanotubes under high current densities ${\text{(>10}}^9 {\mathrm{A/cm}}^{\mathrm{2}})$ show that no observable failure in the nanotube structure and no measurable change in the resistance are detected at temperatures up to $\text{250\hspace{0.05em}°}\mathrm{C}$ and for time scales up to 2 weeks. Our results suggest that nanotubes are potential candidates as interconnects in future large-scale integrated nanoelectronic devices.