tWe have fabricated Ru and Pt nanocomposite films using plasma-enhanced atomic layer depo-sition (PE-ALD), and characterized their structure by means of analytical electron microscopy. Ptand Ru were deposited in Ar/O2plasma using trimethyl(methylcyclopentadienyl) platinum(IV) andbis(cyclopentadienyl)Ru(II) or bis(ethylcyclopentadienyl)Ru(II) as precursors, respectively. The resisti-vity of a Pt film deposited on a Si substrate at 300◦C was 16.2 cm, and that of a Ru film was as lowas 11 cm, showing the film to be metallic and not oxidized. It was revealed that the film prepared bysuccessive PE-ALDs of Pt and Ru on a thin amorphous carbon substrate for electron microscopy analy-sis is a nanocomposite of Ru ribbons and PtRu (7:3) alloy ribbons with 2–3 nm in width. The Ru ribboncomprised small particles with poor crystallinity of the hcp A3 structure and the PtRu ribbon comprisedcrystallites with good crystallinity of the fcc Al structure. The atomic layer deposition would be one ofpotential techniques to produce Ru/Pt nanocomposites for fuel cell catalysts.