Abstract: A device (60) for irradiating blood is provided, the device including a chamber (62) having an elongate configuration defining a hollow interior, the chamber formed of reflective material, a tubular cassette (74) sized and shaped to be received in the interior (70) of the chamber, the tubular cassette (74) having an inside diameter sized and shaped to receive a reflective core (78) having an elongate configuration with an exterior diameter smaller than the interior diameter of the cassette to provide a space (75) for receiving and holding blood stationary, and an array of light-emitting members (80) arranged on the chamber for emitting light of at least one wavelength into the interior (70) of the chamber (62) for irradiating and treating the blood inside the cassette (74).