Many investigators have endeavored to accurately measure oxygen content produced or consumed from substrates or tissues. Most of the techniques currently available are time consuming or exceedingly complex. Many require expensive apparatus and demand the skills of a highly trained technician. We have deveoloped a rapid and sensitive method of measuring oxygen content or consumption. This method is based upon the time for polymerization of acrylamide gels. The time of acrylamide polymerization is directly proportional to the oxygen content of the test medium. We have used this method to generate oxyhemoglobin dissociation curves which closely resemble those published by Severinghaus and Duvelleroy, as well as those we determined by the conventional Van Slyke analysis. We have also used this method to measure the oxygen consumption of tumor cells and to evaluate the effects of Actinomycin, cyclohexamide and cytosine arabinoside on Walker 256 ascites tumor. The results correlate with the known in vivo effects of these drugs on this tumor cell line. Therefore, because of its sensitivity and adaptability this method may be useful in a variety of clinical and biological situations.