Human cytomegalovirus (HCMV) infection induces HCMV IgM antibodies in acute and HCMV IgG antibodies in convalescent phases while HCMV IgG antibodies last for years. Testing for HCMV IgG antibodies as an age-related pattern of infection was studied in Cairo and South London showed that HCMV infection was acquired earlier in life in Cairo than in London. At large 95.6% of 720 sera from the general population in Cairo were seropositive by the age of 5 years compared with 33.3% of 313 sera from British subjects in London. HCMV IgM antibodies were detected only in a small proportion of elderly individuals in both cities. Testing of urine specimens by virus culture showed that congenital infection with HCMV was more common in Cairo (1.28%), compared with (0.0%) in London. Urine samples from 8.6% of Egyptian children aged 2 weeks to 5 years were positive for HCMV by culture, compared with 3.6% aged 6-10 years and 5.8% aged 11-15 years. In children from London, HCMV was isolated from the urines of 11% aged 2 weeks to 5 years, 5.2% of those aged 6-10 years but from none aged 11-15 years.