The active caldera of Campi Flegrei (CF), one of the highest risk volcanic areas on Earth, is located just west of the city of Naples, Italy. The area has been known since Roman times for its hydrothermal activity, intense volcanism and slow, vertical ground movements (bradyseism). Because of its geographical location and long history of habitation and construction, uplift and subsidence at CF have been well documented through time. Several theories have been proposed for the origin of the past volcanism and bradyseism in the caldera. In this contribution, we provide a detailed review of the various models proposed in the past 40 years to explain ground movements at CF. Although several authors propose that the driving mechanism for the accelerated ground uplift at CF can be attributed to an emplacement of magma at shallow depth, evidence does not support this hypothesis. We suggest that in contrast to magma emplacement as a driving force, a hydrothermal model without magmatic recharge is more consistent with bradyseism phenomenon. A hydrothermal model better integrates available petrological, geochemical, and geophysical data with the magmatic-hydrothermal processes at CF.