Using a common cationic surfactant, hexadecyl trimethyl ammonium bromide (HTAB), surface tension at an air-aqueous interface has been investigated as a function of time. Dynamic surface tension data were obtained using a Maximum Pressure Tensiometer (LAUDA MPT 2). The current mathematical model used to describe dynamic surface tension (by Ward and Tordai) predicts that surface tension reduction is a diffusion limited process. The data collected in this study show that surface tension reduction is not a diffusion limited process; there exists some other barrier to surface tension reduction that causes it to be slower than the diffusion limited model. Further investigation is being made into the possible origin of this other barrier to surface tension reduction.