The immotile or dyskinetic cilia syndrome is a disorder of ciliary motility characterized by recurrent sinopulmonary infections, reduced fertility in women, and sterility in men. When situs inversus is encountered, the disorder is referred to as Kartagener’s syndrome. With rare exception, symptoms of the immotile-cilia syndrome can be attributed to an inability of cilia to move at all or to move in a properly oriented and organized fashion. Dynein is a microtubule-associated protein with high molecular weight and high ATPase activity in the presence of magnesium and calcium ions. The dynein arms occupy two rows along the A subfiber of the outer doublet microtubules. Individual arms are spaced at 24 nm within each row. The outer and inner dynein arms of cilia are believed to be the transducers of mechanical force necessary for ciliary motion. The exact relationship between the two dynein arms (inner and outer) and their role in ciliary motility is still unclear.