The ionic reaction products of the title pyridines with iodine in low-density polyethylene are identified by comparison of their IR spectra with literature data. The bis(pyridine)iodine(I), bis(4-methylpyridine)iodine(I), and bis(tert-butylpyridine)iodine(I) cations are spontaneously formed in the polymer medium. At elevated temperature, the 4-methylpyridinium cation is identified as a product of the reaction between 4-methylpyridine and iodine. In spite of their elongated molecular shape, the bis(pyridine)iodine(I) and bis(4-methylpyridine)iodine(I) cations are randomly aligned in stretched polyethylene; they probably form micro-crystalline polyiodide aggregates in the amorphous regions of the polymer. In contrast, the bis(tert-butylpyridine)iodine(I) cation is efficiently aligned in stretched polyethylene.