Nail biting may have a significant role in the development of some anomalies and harmful effects upon the oral-facial system. Objective: The objective of the study was to determine the prevalence of nail biting among preschool children in Bitola. Methods: Through an observational, intersection (cross-sectional) study, 890 children who came to medical checkups during the period from January to December 2009 were included. The following methods were applied: psychological testing (Test of Chuturikj), pediatric examination, interview with parents and the questionnaire: Child Behaviour Checklist-Achenbach, 1981. Results: The study included 890 children, 401 of which were at the age of three, 489 were at the age of five, 51.6% of them were males and 48.4% females. The level of prevalence of nail biting was 22.02%. The statistical analysis showed that the habit is more insignificant (p>0.05) in children at the age of 5 and among the male gender. The tested difference in the frequency of nail biting among children from the cities or villages was not statistically significant (p>0.05). Children who do not have their own room more often manifest this habit statistically insignificantly (p>0.05). Depending on the number of members and children in the family, the tested differences were statistically significant (p<0.05). However, in terms of the order of the child's birth they were statistically insignificant (p>0.05). Children whose parents have a high education level significantly less bite their nails (p<0.01). Increased presence of this habit is found among respondents in families with average incomes, with p=0.004. Conclusion: Dentists and pediatricians should work together on prevention, early diagnosis and treatment of this habit, in order to achieve an impact over dental development.