Background: Esophageal and Lung carcinoma are the leading cause of years of life lost because of cancer and is associated with the highest economic burden relative to other tumor types. Epidemiological studies identify magnesium deficiency as a risk factor for these types of human cancers. The present studies were performed to concerning the contribution of magnesium to tumorigenesis and investigate the concentration of magnesium in esophageal and lung carcinoma. Aims and Objective: The aim of this study was to compare the serum magnesium levels of patients with carcinoma of lung and esophagus patients and apparently healthy people. Material and methods: Study group consisted of 50 clinically diagnosed subjects (Biopsy confirmed 25 cases with Esophageal carcinoma and 25 cases with Lung carcinoma). The control group consisted of 50 healthy subjects were included in the study. Venous blood samples of each lung and esophagus cancer were obtained and serum magnesium level was measured by Atomic Absorption Spectrophotometer measurements. Results: In the study group, we were found mean concentration of serum magnesium was decreased in esophageal (1.40±0.13 mg %) and lung carcinoma (1.23±0.12 mg %) in comparison to controls (2.08 ± 0.45 mg %). Conclusions: Serum magnesium was found statistically significantly lower in study group when compared with control (P<0.0001).