The basic goal of this research was to study the influence of environmental factors on intellectual efficiency of pre-school children. Research participants were 149 children (52 Roma, 48 non-Roma children of average socioeconomic status and 49 children of low socioeconomic status), of the average age of 81 months. Data were collected during maturity evaluation for school in primary schools in Sabac and Sremska Mitrovica. Children's intellectual abilities were assessed by the School Maturity Test, and the data on socioeconomic status and educational climate were obtained from parents, by administering the Questionnaire for collecting data about the child and the family and Interview with the parent. Results of covariance analysis indicated that the quality of stimulation, parental ambitions and financial status of the family have the biggest effect on intellectual achievement of children. Poorer cognitive efficiency is demonstrated by children who grow up in poverty and non-stimulative environment, and whose parents have low ambitions regarding their child's education. When these variables are controlled, there are no differences between groups in either of cognitive functions. The abilities of visual and motor coordination and attention proved out to be the most sensitive to the influences of environmental factors. The results indicate that environmental factors have a pervasive effect, since, besides the influence on manipulative abilities, they also determine achievement on tests used to estimate verbal abilities.