Immunity to measles virus, rubella virus, and mumps virus was determined by EIA in serum samples and in dried whole blood specimens spotted on Whatman filter paper (5 mm in diameter). Both specimens were obtained from each patient by venepuncture and finger prick. Ten microliters of whole blood is enough to detect antibodies to these three different viruses. The comparison of the results obtained by EIA from 227 serum and whole blood samples have demonstrated close agreement: 98.6% for measles virus, 99.1% for rubella virus, and 96.0% for mumps virus. Moreover, 96 whole blood samples can be tested in a microtiter plate and can be stored at room temperature for 15 days or at +4 degrees C for several months. Therefore, whole blood dried on filter paper is a convenient alternative method for collecting and transporting specimens, it is easier and safer than venepuncture, and could be used for large-scale epidemiological studies, especially in newborns. This method could solve the problem of sampling, especially in young children, and could simplify studies of vaccine efficacy.