Forty low-birthweight (LBW) infants (28 AGA, 12 SGA) and 16 fullterm infants have been followed for three years with neurological, developmental, language, behavior and audiometric assessments. Only two (5 per cent) of the LBW infants were neurologically abnormal at three years. The AGA infants continued to lag cognitively and in receptive language in comparison with the fullterm infants. Socio-economic factors had a significant effect on the language development of all three groups. Short gestation and neurological status at eight months continued to have a significant effect on language performance. A variety of behavioral characteristics correlated with cognitive and language scores, and impaired middle-ear status was associated with lower cognitive function. These data support the concept that language development of LBW infants is influenced by perinatal, neurological and socio-economic factors, and by behavioral characteristics and middle-ear status.