The longitudinal series of measurements of general and linguistic ability from 6 months to 8 years of age, reported in Part I, have been related to a number of environmental variables. Significant correlations were found with social class, mother''s vocabulary, ordinal position and ratings of the stimulus quality and emotional climate of the home at 2 1/2 years; not with maternal age. Analysis of the spacing of older and younger siblings yielded inconclusive results. Children who had had daily substitute mothering from an early age tended to be retarded in reading, though their other abilities were not significantly affected. Contrasting patterns were found for boys and girls, suggesting that girls may develop better with maternal care and profit from gaining a younger sibling, while for boys the contrary may be true. The early ratings of the home turned out to predict ability at 8 years better than at intervening ages, and significant relationships remained when social class was held constant. Indeed the quality of the home during the period of language acquisition, together with social class and ordinal position, would appear to offer a basis for prognosis of later ability as good or better than that achieved by scales of development in the first 2 years.