A simple two item developmental screening test for three year old children is described, together with its predictive validity when used with 937 children being followed in the Dunedin Multidisciplinary Child Development Study. Data are presented to show that the test screened out 6.9 percent of the three year old children and more than half of them gained very low scores on at least one test of intelligence, motor or language development two years later. The screening test successfully identified from one half to three-quarters of all the children who gained very low five year scores in intelligence, motor or language development at age five. The two item screening test is recommended for use by doctors, nurses, teachers or social workers, as a simple method of identifying three year old children in need of further assessment because of suspected developmental delays.