In order to determine the underlying mechanism of the proliferation inhibition mediated by the application of 4.5 mT - 120 Hz ELF-EMF, we investigated the effect of this application on cyclin D1 expression, a cell cycle regulator protein responsible for the transition from G1- to S-phase in both normal regulation of the cell cycle and development of human cancers [18]. The gene discussed is CCND1; the disease is cancer.