Neutralizing antibody (NA), hemagglutination inhibition antibody (HI), and antibody assayed by IgG-enzyme immunoassay (EIA) against measles were tested as a set on sera of 119 out of 120 patients institutionalized for severe motor and intellectual disability and correlations among the 3 types of antibody titers were examined. 1) NA, HI, and EIA titers correlated positively. 2) If NA, HI, and EIA antibody titers were 4 (2(2)) or more, NA, HI, and EIA serum titers were positive. If they were 8 (2(3)) or more, all sera were positive for NA. If light absorption was 4 or more, serum HI was also positive for EIA. 3) Nine cases were certified as positive for measles infection, and 3 of these were vaccinated 2-3 years after infection. All 9 had positive NA and EIA even 15 years or more after infection. Of 29 cases certified as negative for measles infection and injected with measles vaccine, 21 (72.4%) had positive NA and 16 (72.4%) had positive HI. In EIA, 28 of the 29 (96.6%) showed positive. The only EIA-negative case was also the only one negative for both NA and HI, i.e., an 18-year-old man suffering from chromosomal aberration, 21-ring trisomy, and suspected of being a low responder to measles antigens, including NA, HI and EIA antigens. 4) The above facts suggest that EIA is a more sensitive test for positive history of wild measles virus or measles vaccine virus contact, making it possible to detect measles or measles vaccine injection. To prevent nosocominal infection, it is important to know whether institutionalized individuals are immune to measles, but many have no clear history of measles or measles vaccine injection, especially those 40 years old or older. 5) Institutionalized individuals 40 years old or more numbered 45. Their antibody titers against measles were positive, 82.2% in NA, 48.9% in HI and 91.1% in EIA. The high positive EIA rate suggests that most would sufferered from measles before institutionalization, because they had little chance of measles vaccination as children and little possibility of measles infection in the institution at nosocomial infection currence in 1983, which was limited in other ward, and no nosocomial infection of measles has been experienced in this institution during this more than 20 years.