In recent times, the incidence of allergic diseases, particularly bronchial asthma, has been increasing worldwide. However, there appears to be no published data on the prevalence of allergic diseases among school children (3 to 16 years of age) in Karachi, Pakistan, with only limited data available among few age groups under one ISAAC study. The objective of this project was to investigate the prevalence of allergic diseases among school children (3 to 16 years of age) in the city of Karachi. The questionnaire that was used for data collection had previously been used for a similar study in neighboring Saudi Arabia and the U.A.E. In 2007, a total of 3,000 surveys were distributed in various schools of Karachi, of which 2,325 completed surveys were obtained. SPSS was used to perform statistical analysis on the collected data. Survey results showed that the frequency of diagnosed (previously seen by physicians) cases of asthma stood at 15.8%, while the frequency of allergic rhinitis was found to be 28.50% among these children. Other parameters that were analyzed included dry cough (20.1%), wheezing (11.7%), breathlessness (15.40%), and eczema (21.8%). Furthermore, smoking by family members was found to be associated with asthma (p value less than 0.05), allergic rhinitis (p value less than 0.05), breathlessness (p value less than 0.05), dry cough (p value 0.002), and wheezing (p value less than 0.05). This study reveals that there is a significant number of school children in the metropolitan city of Karachi who have various allergic symptoms. It also sheds light on the fact that exposure to indoor environmental factors as well as family atopy can play a key role in increasing the chances of an individual to experience asthma and other allergy symptoms.