Molecularly ordered composites of polyvinylimidazole-[Os(bipyridine) 2 Cl] (PVI-[Os(bpy)2Cl]) and glucose oxidase (GOD) are assembled inside a fi lm of aligned carbon nanotubes. The structure of the prepared GOD/PVI- [Os(bpy)2Cl]/CNT composite fi lm is entirely uniform and stable; more than 90% bioelectrocatalytic activity could be maintained even after storage for 6 d. Owing to the ideal positional relationship achieved between enzyme, mediator, and electrode, the prepared fi lm shows a high bioelectrocatalytic activity for glucose oxidation (ca. 15 mA cm-2at 25 °C) with an extremely high electron-transfer turnover rate (ca. 650 s-1) comparable to the value for GOD solutions, indicating almost every enzyme molecule entrapped within the ensemble (ca. 3 × 1012enzymes in a 1 mm × 1 mm fi lm) can work to the fullest extent. This free-standing, fl exible composite fi lm can be used by winding on a needle device; as an example, a self-powered sugar monitor is demonstrated.