Background: Asthma remains an increasing cause of morbidity and mortality in adults, especially in developing nations. In Libya, no previous study has reported the diagnosis of asthma among adults. The primary objective of this work is to validate the diagnosis of asthma through a survey questionnaire for adult Libyans, by using a digital spirometer as a recommendation to diagnose asthma. The specific objective of this study included the search for a correlation between asthma symptoms and its diagnosis. Materials and Methods: An adapted International Study of Asthma and Allergies in Childhood questionnaire was distributed to 1800 participants >18 years. Results: Females comprised 56.7% of the sample. Pulmonary function tests (spirometry) were performed on respondents who reported wheezing and chest tightness at rest and during daily activity. Approximately, 17.6% of the participants reported having wheezes during the past 12 months, while 18.4% had chest tightness at rest and during daily activities. A significant correlation was found between wheezing and chest tightness (P < 0.001). About 44% of the participants showed a positive reversibility test. Conclusion: Chest tightness at rest and wheezing are more reliable for diagnosing asthma. The city of Sirte in Libya requires the establishment of the common pollens which trigger asthma.