RNA polymerase I (Pol I) exclusively transcribe the ribosomal RNA (rRNA) which constitutes the vast majority of the total cellular transcription products. Furthermore, rRNA synthesis is highly related with cell division, growth and biogenesis. Previous studies demonstrated that there is a high correlation between rRNA level and the rate of protein synthesis in the cell [1, 2]. Therefore, the activity of PoI I is highly regulated during the cell cycle because of the energetic cost of protein synthesis. However, the precise activity and the mechanistic pathways of Pol I during transcription are still unknown. Here, we investigate the kinetics of Pol I transcription using the Tethered Particle Motion (TPM) technique. Unlike optical and magnetic tweezers, TPM allows observation of transcription in the absence of tension applied to the DNA template [3]. We also verified that the Upstream Activation Factor (UAF) is not required for basal in vitro transcription, in coherence with previous reports [4], transcription did not occur without Tata Binding Box Protein (TBP) and core factor (CF) proteins. We measured transcription rates, at different nucleotide concentrations, which are comparable with those previously reported from in vitro bulk studies.