Resumo. ABSTRACT The relationship between metabolic acidosis and athletic performance has been investigated over the years through manipulation of the blood and muscle pH. Among the pH manipulation manners, the ammonium chloride (NH4Cl) is the most widely used chemical component when is intentioned to induce a blood acidosis status prior to exercise. However, there is a lack of studies investigating the action of this substance on athletic performance as only two studies were performed in the last 15 years. Thus, it will be addressed in the present review the main aspects involved in NH4Cl ingestion, giving a focus to the action mechanisms of this substance, specifications about the used dose and their effects on athletic performance.