81 milk samples collected from 35 donors 3 days to 7 months after delivery were examined for the occurrence of cytomegalovirus (CMV). 30/35 (89%) of the women were seropositive to CMV. The virus was only found in samples from seropositive women collected greater than 8 days to less than 3 months after partus. During this period milk from 23 seropositive donors were tested; 16/23 (70%) excreted CMV. CMV is evidently a very common finding in the milk of seropositive mothers.