Background: The adolescent girls are more vulnerable, particularly in developing countries including India, due to various adverse socio-cultural and economic reasons. Majority of the health problems affecting adolescent girls are preventable by promotion of hygienic practices through proper health education by the teachers. Aim: This study was designed to examine the various factors influencing the prevalence of morbidity among school-going adolescent girls of Lucknow district in north India. Materials and Methods: A cross-sectional study was carried out in urban and rural schools of Lucknow district from 2008 to 2009. Multistage random sampling was used to select the requisite number of girls. A total of 847 adolescent girls between 10 and 19 years of age were interviewed, and information regarding their socio-demographic characteristics was collected and clinical examination was carried out. Statistical analyses were done using percentage and Chi-square test. Results: Of 847 adolescent girls, around 64.8% were found to be sick at the time of the study. Significant association of morbidity was observed with caste, birth order, type of family, socioeconomic status (SES), living status with parents/guardian, and general personal hygiene (P<0.05). Conclusion: This study reveals a high prevalence of morbidity. A strong need exists for planning and programming intervention activities for health needs in the area.