According to quasigeostrophic theory, the formation and intensification of a sea-level anticyclone is due to the advection of anticyclonic vorticity in the middle and upper troposphere. However, this vorticity advection is also associated with subsidence and attendant adiabatic warming which, thermodynamically, would lower sea-level pressure and weaken the sea-level anticyclone. This paradox is reconciled through the development and application of a new conceptual model for sea-level anticyclogenesis, derived from principles of hydrostatic balance and thermodynamic energy. According to this model, the sea-level pressure rises associated with anticyclogenesis are due to vertically integrated cold-air advection and/or diabatic cooling. It is hypothesized that upper tropospheric cold-air advection is the primary mechanism for sea-level anticyclogenesis, since temperature advection is small over the incipient anticyclone in the lower and middle troposphere, while diabatic processes are negligible throughout the troposphere over the sea-level anticyclone center. This hypothesis is confirmed by model calculations for several cases of sea-level anticyclogenesis selected from atmospheric analyses.