Introduction: The association of asthma and obesity appears as a phenotype in its own right with its own biological characteristics. It is characterized by a low-grade systemic inflammation involving adipokines such as leptin, which has a close relationship with vitamin D, whose levels are relatively low in obese subjects. The objective of this study is to determine the role of vitamin D in the expression of inflammation in the asthma-obesity phenotype. Material and methods: This is a cross-sectional study carried out at the physiology laboratory of the University Hospital of Batna during one year in 99 patients among whom 67 subjects are obese and 32 non-obese. Blood samples were taken to measure the levels of leptin, IL6, vitamin D, CRP and fibrinogen. The measured biological parameters of the two groups "obese" and "non-obese" were compared. The data were entered and analyzed with SPSS® software. Results: The asthma-obesity phenotype of the population is characterized by systemic inflammation dominated by elevated levels of leptin and interleukin 6 compared to "obese" controls. There is an inverse relationship between blood vitamin D levels and BMI, and a negative correlation between leptin levels and serum vitamin D levels was found. Conclusion: The association of asthma with obesity is characterized by a particular biological profile of systemic inflammation modulated by insufficient vitamin D levels. Key words: Asthma, obesity, phenotype, inflammation, adipokines.