Presence of cytomegalovirus (CMV) specific immunoglobulin M (IgM) is generally considered strong evidence of current or recent CMV infection. Sera from 110 elderly individuals (age range 61-100 years) were compared with sera from 87 younger individuals (age range 16-47 years). Prevalence of CMV IgM was found to be 30% in the older group (mean age 83 years) and only 6% in the younger group (mean age 29 years). In spite of increased CMV antibody levels, none of the elderly individuals were symptomatic. Viral cultures of urine from 72 elderly individuals were negative for CMV. These results suggest that the presence of CMV-specific IgM must be interpreted with caution in an elderly population.