The need for and the commercial pressure to develop and market effective masking agents for athletes using androgenic hormones motivated this study. This paper presents the results of a novel masking agent when used in conjunction with testosterone cypionate. It is also the first paper that follows an open approach and makes a covert process available to the scientific community. A sample of 26 elite marathon athletes completed the trial. The experimental group (n = 12) received the 4ml testosterone cypionate with one 8ml novel masking agent over six weeks. The results have shown that the testosterone cypionate significantly increased muscle mass, weight gain, and running time compared to the control group (p < .05). Four participants showed adverse reactions during the trial and the marathon race. Post-marathon testing for banned substances showed that the masking agent is 66% effective. Future studies could consider adding sedative-analgesic to reduce discomfort during the administration of the cypionate and the masking agent.