The ventilatory anaerobic threshold (VAT) occurs when there is an isolated increase in the slope for ventilator equivalent for oxygen consumption (VE/VO2) with no change in the slope for ventilatoiy equivalent for carbon dioxide production (VE/VCO2) when both are plotted against time. The concept of anaerobic threshold remains controversial. However, it is a clinically useful tool in evaluating the exercise capacity of children. This paper will review the history, biochemistry, and methodology involved in determining the anaerobic threshold, as well as the ventilatory anaerobic threshold in children.