Aim: To shorten orthodontic treatment times by improved biomechanics and monitoring, and to combine these with orthopedic effects. Methods: These aims are enabled using ultralight forces that provide rapid bodily tooth movement when appropriately combined with standard orthodontic forces in fixed appliances. The study of the various orthodontic elements in terms of their rate of tooth movement will be called rheodontics (rheo = flow). The unimpeded part of rheodontics will comprise part I as the essential starting point. Results: First, ultralight forces permit many elements of treatment to be done concomitantly, such that overjets may be routinely reduced bodily at 1.5 mm per month with 2-oz elastics, while simultaneously bringing canines bodily out of the palate in 4 months. Second, by using ultralight forces, parafunctional effects are more obvious, which is more an advantage than a disadvantage. As part II will show, the correct diagnosis and release of parafunctional ankylosis, as it may be called, can have dramatic effects on the speed of the various elements of orthodontic treatment and is kinder to hard and soft tissues than heavier forces. Parafunction is more often the cause of extended treatment times than noncompliance. Third, part III will show how orthodontics may be combined at will with certain orthopedic effects with the same fixed appliance. Conclusion: The integration of all details, especially ultralight forces and good functional occlusion, is essential for rapid and good results. World J Orthod 2000:1:98–104.