BACKGROUND Children with language problems are found to have a higher risk for future academic difficulties and learning disabilities. Conclusions from related literature were in many ways inconsistent. OBJECTIVE To identify systematically, the existing literature, and factors that influence language development in children. MATERIAL AND METHOD Databases of scientific literature were screened through the internet for publications that involved factors effecting language development in childhood. Hard copies of related scientific journals were also sought for relevant topics by the authors, making use of reference lists of publications, and citation search. Studies were included if they were published since 1984 and investigated factors that affect language development in children. They were excluded if they were not original research articles. RESULTS Fifteen studies were included for this review--a case-control study, a cross-sectional study, and thirteen longitudinal studies. Most studies demonstrated that the following factors affect language development--antenatal care, Apgar scores, birth weight, premature delivery, birth order, parental education, environmental factors, gender of the children, and family history with specific language impairment. CONCLUSION Perinatal/postnatal and environmental factors influence language development. Such factors should be taken into account as confounding factors in further language development studies.