The present work describes new effects in the kinetics of the electrochemical oxidation of silicon observed recently by the author. One is the observation of very large oscillations of anodic potential during anodization of silicon in H3PO4/HF electrolyte and another is the effect of externally applied mechanical stress onto the kinetics of the Si anodization in concentrated and diluted HF. We show that besides of purely electrochemical factors influencing the kinetics of the Si reaction with electrolyte solutions (oxidation of the semiconductor and its local dissolution) one should include into consideration the effects of mechanical stress which builds in during the electrochemical treatment of the semiconductor. We show that the critical voltage and current values observed in I-U polarization curves are influenced not only by the electrochemical activation/passivation reactions but also by morphological factors.