SUMMARYA series of 480 children was investigated by scintiscanning between 1966 and 1975 by rectilinear scanning or by gamma camera imaging. Of this group 39 were reported abnormal in the posterior fossa region–10 were reported as normal but were found subsequently by other investigations or by operation to have a lesion in this region. Of the 39 reported abnormal 37 were subsequently found to have a lesion, either benign or malignant. There were 2 false positives. The overall accuracy of diagnosis in the posterior fossa was 75.5%.The value of cerebral radionuclide imaging in the study of posterior fossa lesions in children has been upheld. The investigation is non invasive, safe and reasonably accurate and is an important screening test in this are