Solar cycle variations of the internal structure and dynamics of the sun

Helioseismic analysis of solar global oscillations allows investigation of the internal structure and dynamics of the sun. I summarize the recent observational results, putting emphasis on the bands of slower- and faster-than-average rotation migrating in latitude over the solar cycle in a manner similar to the zones of solar activity. I also review theoretical considerations so far proposed as a cause of the periodic oscillation of the rotation profile.