Cytomegalovirus (CMV) disease is a major problem in renal transplant recipients, but few predictive markers of the disease are known. Several immunologic parameters of potential relevance for the defense against CMV were measured after renal transplantation in 25 patients before any manifestations of CMV infection occurred. In 10 patients who later developed CMV disease, plasma levels of interleukin-8 were significantly higher, whereas the levels of macrophage inflammatory protein-1alpha (MIP-1alpha) were significantly lower than in 15 patients who did not develop CMV disease. Also, lower numbers of CD4+ and CD8+ lymphocytes were observed in patients who later had CMV disease. These findings were independent of previous rejection therapy and were particularly pronounced in patients with primary CMV infection. Interleukin-8 and MIP-1alpha may be predictive markers of CMV disease and could be of potential use in selecting patients for prophylactic treatment.