The "carbide treatment" hastens the ripening processes of thoroughly green bananas as shown by the rates of softening, respiration, starch hydrolysis, flavor and color changes. That these effects are due to acetylene rather than ammonia or some other impurity in the gas seems fairly well established by the experiments in which the gas was purified. It has not been shown that no ethylene was present in the acetylene, but it seems very unlikely in view of the conditions under which the gas was produced and purified, and the low concentration of acetylene used in some experiments. There appeared to be no sharp limits to the concentrations of acetylene giving these results. Though the difference in the respiratory rate may be considerably increased at a given time by the treatment, the maximum respiratory rate during the ripening may not be greatly changed by the treatment except in the case of severely chilled fruit. The effect appears to be mainly in the abbreviation of the period of low activity normally occurring at the beginning of the ripening processes or which may be considerably extended by unfavorable conditions such as chilling. The condition of the fruit at the beginning of the experiment is of prime importance as to the results obtained. It is suggested, that the high initial respiratory rates determined by previous workers were due to the fact that the fruit was well advanced in the ripening processes, at the beginning of the experiments, due either to exposure to favorable ripening conditions, or to stimulation by ethylene, acetylene or other volatile substances of similar action. The results with acetylene are in agreement with those obtained with ethylene, and also with its previously determined effects on horticultural material.