Abstract: A reactor system especially suited for removal of chemical species from the bloodstream or other biological solutions containing suspended material. The reactor contains species such as enzymes, antibodies, receptors, anti-toxins, and a variety of drugs or inorganic compounds immobilized on particulate supports and/or solid phase adsorbents which react with specific materials under the appropriate conditions.The reactor chamber is cylindrical and may optionally include a second cylinder internal to, and concentric with, the first cylinder, where the annular space between the pair of concentric cylinders forms the fluid path. The reactor chamber is oscillated through an arc of between approximately 50 and 90 degrees along an axis perpendicular to the axis of the flow of fluid through the reactor.