Helioseismic data show temporal variations that are clearly related to the solar cycle.
The frequency variations seem to be mainly due to near surface effects, but the physical relation between these variations and the surface magnetic fields has not been established yet. With GONG operating for over 3 years by now and SOHO for 2 years, we have data sets available which continually cover the end of solar cycle 22 and the beginning of solar cycle 23. This allows us to study the solar cycle variation of p-mode parameters with unprecedented detail. I will discuss recent results and some of their implications.