The present paper highlights the development of organic nanowires from small-molecular organic compounds through intra-track chemical reactions by using ion beams. Thin films of pentacene derivatives, 6,13-bis(triethylsilylethynyl)pentacene (TES-Pn) and 6,13-bis((triisopropylsilyl)ethynyl)pentacene (TIPS-Pn), were subjected to high-energy particle irradiation at a fluence of 10 8 –10 10 cm –2 and thereafter developed by organic solvents. This method, referred as Single-particle Triggered Linear Polymerization (STLiP), afforded the isolation of wire-shaped nanomaterials on a substrate that were visualized by atomic force microscopy and scanning electron microscopy. These derivatives exhibited high enough propagation and cross-linking reaction efficiencies (G) as GTES-Pn of > 7 and GTIPS-Pn of > 5 (100 eV) –1 , whose values are significantly larger than those observed for previously studied simple cross-linking reactions observed in other polymeric materials, being apparently in the G-value range of chain reactions. On the other hand, the pristine pentacene and derivative without (trialkylsilyl)ethynyl moiety did not give any nanowires. Considering these observations, highly efficient intra-track propagation/polymerization/cross-linking reactions would take place due to the introduction of (trialkylsilyl)ethynyl groups, resulting in the formation of one-dimensional nanostructures based on small molecules. The STLiP technique serves as a versatile and easy nanofabrication tool for small molecular materials and the resultant nanowires with high functional density are potentially usable as optical, electronic, and sensor materials.