Abstract
By serological investigation of various groups of patients, a correlation was found between rise in titre of antibodies to cytomegalovirus (CMV) and rise in cold agglutinin (CA) titre. This correlation was most marked, and significant, in a group of renal graft recipients where 16 of 27 had roughly parallel rises in CA and CMV antibody titre. It is suggested that in most patients showing this correlation the production of CA was related to infection with CMV, and it is possible that this immunological feature is more common in patients with CMV pneumonia.