Hypertension results from an interaction of many risk genes and environmental factors. The M235T allele of the angiotensinogen gene is thought to increase plasma levels of the angiotensinogen which is associated with hypertension. The angiotensinogen is an important substrate for renin in the RAAS that is finally converted into angiotensin II that plays a key role in the control of blood pressure. This study was designed to measure plasma angiotensinogen levels in an adult population in Calabar and Uyo (South-South), Nigeria in relation to the M235T allele and hypertension. Out of a large population of 1224 participants who had been genotyped for the M235T polymorphism, plasma was collected from a sample of 300 consisting of 150 patients and 150 controls. Protein A sandwich enzyme linked immunosorbent assay was carried out with the plasma samples to measure the angiotensinogen levels. Age, BMI, M235T allele, blood pressure and O.D values were compared between controls and patients using the independent t test. The absorbance values of plasma angiotensinogen were significantly higher in the patients (0.71) with M235T allele than in the controls (0.53). Further research still needs to be carried out to determine the actual concentration of the protein in the participants.