The plasma pressure calculated from the force balance equation in the Tsyganenko magnetic field model under quiet conditions is found to be in good agreement with the observed pressure distribution in the central plasma sheet. This result indicates that the central plasma sheet can exist without a minimum-B region in a quasi-steady state. The plasma density and temperature measured by AMPTE/IRM in the central plasma sheet under quiet conditions fall in between the predictions of the adiabatic equation of state and the isotropized magnetic-moment equation of state. A hybrid equation of state derived from a simple combination of the adiabatic equation of state and the magnetic-moment equation of state is shown to be in excellent agreement with AMPTE/IRM data. ¿ American Geophysical Union 1992