The importance and consequences of raising the average ability level (IQ) of the population requires consideration of the ability level that society requires, how the relevant abilities are distributed, and the efficiency of the current educational process. Within the framework of these factors, the document discusses the determinants of mental ability and the measures commonly used, the sources of variance in IQ, and the ways in which intelligence might be boosted. The latter include both genetic and non-genetic influences. Such prenatal factors as nutrition, length of pregnancy, maternal stress, and intrauterine environment have and effect on infant intelligence. Postnatal environmental influences have not been found to markedly affect IQ, with the exception of extreme isolation. In relation to disadvantaged children, whose learning and ability patterns are different from those of middle-class children, it is important that these differences be recognized as a precondition to developing appropriate educational strategies. (NH)