Background: Magnesium (Mg) is an intracellular cation which takes part in various functions including smooth muscle contractility. Studies have shown that serum Mg level has no significant effect on asthma severity. To evaluate serum magnesium levels in asthmatic subjects. Materials & methods: A total of 40 subjects were enrolled. They were divided into 20 cases and 20 controls. The subjects with respiratory medicine with stable asthma were randomly selected. The statistical significance was calculated using Chi-square test. The result was analysed using SPSS software. Results: There was a linear relationship between serum magnesium level and FEV1. As the FEV1 decreased, there was an associative decrease in serum magnesium levels. Conclusion: Hypomagnesaemia is more prevalent in stable asthmatics. Keywords: Magnesium, Asthma, Serum hypomagnesaemia.