Two sets of experiments consisting of 1 hr- and 4 hr- transportation were undertaken to examine effects of road transportation of calves on their cellular immunity. From the results obtained, it is concluded that the calves transported by road fall into disorders of lymphoreticular cell functions, and that sera from the calves after transportation impair activities of normal lymphocytes and alveolar macrophages obtained from healthy donors. The cell and serum disorders may play an important role in the pathogenesis of respiratory tract disease complex, knows as shipping fever.