Diamond film growth without seeding treatment has been the subject of numerous studies. In this study, diamond films with/without seeding treatment were grown on silicon using hot-filament chemical vapour deposition. An inexpensive and simple approach, namely 'dry ultrasonic treatment', was introduced in which full coverage of the diamond film was achieved over the substrate having no prior seeding treatment. For comparison purposes, two substrates were seeded with different sizes of diamond particles, 5 mu m by hand and 30-40 mu m by ultrasonic agitation, prior to deposition. The produced diamond films were examined through standard characterization tools and distinct features were observed in each film. The diamond film grown without the seeding treatment shows slightly lower growth rate (1 mu m h(-1)) but bigger grain size up to 8 mu m compared with seeded films. Here we show the growth of uniform and high-purity diamond films free from nano-sized grains, which are grown without any seeding treatment.