The homologous series HgBa2Can-1CunO2n+2+delta (n = 1, 2,3,4) are the newest and most promising of the layered high-T(c) superconducting materials, as demonstrated in setting the highest T(c) among the known superconducting materials. The first of its series, HgBa2CuO4+delta, contains only one Cu-O plane per unit cell and is superconducting with T(c) about 94 K. The superconducting transition temperature as a function of pressure, T(c)(P), was measured to 4.5 GPa. T(c) was determined from ac susceptibility measurements and pressure was determined near T(c) from shifts in ruby fluorescence peaks. T(c) increases monotonically with dT(c)(P)/dP almost-equal-to 1.8 K/GPa at ambient pressure. The volume as a function of pressure, V(P), was measured to 10 GPa. The lattice parameters were determined by energy-dispersive x-ray-diffraction methods and pressure was determined from shifts in ruby fluorescence peaks. The volume decreases monotonically producing an isothermal bulk modulus B(V) = 104 +/- 17 GPa at ambient pressure. Both results were combined to produce T(c)(V), which is more readily compared to theoretical models.