This study was conducted on 5554 children aged 5-13 years old with the objectives of recording the prevalence of oral habits among North Indian children according to sex. These children were selected from the schools of Delhi. The sample represented the entire school-going population of Delhi in the age group of 5-13 years. Statistical analysis was carried out using BMDP software and sex differences were calculated by using Fisher's exact test. The results showed that the prevalence of oral habits in Delhi school going children was 25.5%. Tongue thrust was the commonest habit (18.1%) followed by mouth breathing (6.6%). Thumb sucking was relatively less common habit and seen in only 0.7% of children. There were no significant differences between boys and girls for the prevalence of oral habits. However, for the specific habit types there was a sex difference. Thumb sucking was more common in girls (1.0%) when compared with boys (0.4%) and this difference was statistically significant (P < 0.001). There was a reverse trend for the mouth breathing, which was more common (P < 0.001) in boys (7.8%) than girls (5.3%). There were no differences for tongue thrust habit between boys (17.5%) and girls (18.6%).