Abstract
An analysis of the clinical value of radioisotopic lung function (RLF) tests has been carried out on the results of studies in 123 children with heart or lung disease. The overall incidence of useful RLF tests was 53%, but in children between 6 months and 6 years the incidence was higher (69%). The incidence of useful RLF test was similar whatever the question to be answered, although rather higher when information about differential pulmonary blood flow was required. Lists of conditions are presented for which the incidence of useful RLF tests is likely to be high (72%), moderate (46%), and low (14%).