Introduction: Stereotypic behaviors are characterized by repetitive, deviated and aimless actions that persist for more than 4 months in individual. Nail biting habit is one of informed obsessive-compulsive disorders that begins in childhood and continues for a long time. Onychophagia is a disorder with unknown cause and many factors can predispose it in a child. Individual characteristics and environmental factors are among other factors that may cause onychophagia in a child. Materials and Methods: In this cross sectional study prevalence of nail biting in 600 male and female students of primary schools of Kerman has been assessed. Results: The prevalence of nail biting was 28.7% and the duration of onychophagia was between 1-2 years in 53.5% of cases. Onychophagia was most common in age group of 13 years. IQ, grade, success in exams, parents job and association with other stereotypic habits were evaluated. Nutrition in infancy period, position of labor, parents’ educational level, and family population were also analyzed. No significant relation was found between any of above factors and nail biting. Conclusion: Nail biting can be considered as an independent and temporary event in the growth period of child.