The electronic properties of porphyrin zinc aggregates wired using single-walled carbon nanotubes (SWNTs) are described. A self-assembled structure is formed by casting a solution of SWNTs and 5,15-bispentylporphyrinato zinc(II) (BPP-Zn) onto a substrate (see figure). Rectifying behavior has been observed at SWNT/BPP-Zn junctions, although no rectification is seen for bare SWNTs. The results show that aggregates of even a few BPP-Zn molecules work as a rectifying device with SWNT wiring.