Abstract Final products in the radiolysis of pure neopentane at 4 and 77 K have been analyzed by capillary gas chromatography. The results are inconsistent with those obtained by esr spectroscopy. The ratio C-C to C-H bond rupture in the radiolysis of neopentane is 0.3–0.5 from the product analysis at 4 and 77 K while esr spectroscopy at 4 K indicates an extremely low ratio (<0.01).