A new epithermal neutron source is proposed for boron neutron capture therapy (BNCT). The use of epithermal instead of thermal neutrons for BNCT is advantageoud due to the greater penetration depth of epithermal neutrons in tissue which results in skin sparing during tumor irradiation. Epithermal neutrons are produced by bombarding a lithium target with an intense proton beam from a Cascade Tandem Accelerator (CTA). The CTA is a novel electrostatic accelerator which combines two existing technologies into a simple, compact proton accelerator suitable for operation in a hospital environment. Preliminary calculations indicate that a 1 mA, 2-2.5 MeV proton beam incident on the target will provide sufficient epithermal neutron flux for biological studies and for tumor irradiation. In this study, target and neutron moderator geometry will be modelled using Monte Carlo techniques to determine the optimum target assembly design and proton beam parameters. This system will be capable of providing a wide range of neutron energy spectra, intensities and irradiation times for both laboratory and clinical BNCT studies.