Close examination of restriction enzyme digest profiles of cytomegalovirus (CMV) isolates from corecipients of organs from a common donor revealed instances of intermittent or prolonged shedding of two strains transmitted from the same donor organ. In two corecipients, two distinct donor strains were isolated by end-point dilutions of urine specimens or of cell-free virus stock and were shown by monoclonal antibody staining to differ in their major immediate-early antigen. The separated strains retained stable restriction profiles through >20 passages in cell culture. However, similar passage of the original mixed-strain clinical isolates gave rise to new, recombinant strains of CMV. These findings indicate that more than one strain of CMV can establish latency in normal hosts and suggest that new viral strains arise readily through recombination of existing strains.