A compact and efficient lightpipe device to deliver light to the human oral cavity for photodynamic therapy was designed and fabricated, having dimensions $6.8\text{\hspace{0.17em} mm}\times 6.8\text{\hspace{0.17em} mm}\times 46\mathrm{mm}$ . An average irradiance of $76\mathrm{mW}/{\mathrm{cm}}^2$ with an average deviation of 5% was measured on a square $25{\mathrm{mm}}^2$ treatment field for an input power of $100\mathrm{mW}$ . The device limits irradiation of healthy tissue and offers potential for improvement over the current treatment procedure, which requires shielding of the whole cavity to avoid damage to healthy tissue.