Highly uniform, smooth nanocrystalline diamond films have been fabricated with a magnetoactive microwave chemical vapor deposition system. The top and bottom magnet currents were 145 and 60 A, respectively, while the microwave power and substrate temperature were controlled at 1500 W and 850-degrees-C, respectively during deposition. The total processing pressure was regulated at 40 Pa (300 mTorr) with gas-flow rates of 30 sccm of hydrogen, 2.4 sccm of methane, and 1 sccm of oxygen. Diamond films obtained under these conditions have grain sizes between 0.1 and 0.3 mum, and a mean roughness of 14.95 nm. The growth rate is 0.1 mum/h. Characterization techniques have involved x-ray diffraction, Raman spectroscopy, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. Both x-ray and electron diffraction patterns show no evidence of graphitic phase. Although a high density of twins and stacking faults was revealed by high-resolution electron microscopy, compact diamond grains, and clean intergranular boundaries (no graphitic phase) were observed.