A considerable controversy has developed as to the value of the 32 p uptake test in the diagnosis of intraocular tumours. As Shields (1978) stated, clinicians who have great experience with this test have stressed its accuracy in differentiating benign from malignant intraocular tumours but have perhaps failed to stress its limitations adequately. On the other hand, some clinicians with authority have doubted the usefulness of the 32 p test. Their opinion, however, was not based on valid statistical data but on incidental findings of false-negative and false-positive results. Like any other diagnostic test in medicine, the a2p test is not 100% reliable, has its limitations and can only be evaluated by statistical analysis of controlled studies of sufficiently large numbers of patients. We had the opportunity to carry out an extensive study thanks to the cooperation of the ophthalmologists in the Netherlands and of the Netherlands Ophthalmic Research Institute.