Using a novel NMR scheme we observed persistence in 1-D gas diffusion. Analytical approximations and numerical simulations have shown that for an initially random array of spins undergoing diffusion, the probability p(t) that the average spin orientation in a given region has not changed sign (i.e., ``persists'') up to time t follows a power law t^{-\theta}, where \theta depends on the dimensionality of the system. The large nuclear spin polarization of laser-polarized 129Xe gas allowed us both to prepare an initial ``quasi-random'' 1-D array of spin orientations and then to perform real-time NMR imaging to monitor the spin diffusion. Our measurements are consistent with theoretical and numerical predictions of \theta ~ 0.12. We also observed finite size effects for long time gas diffusion
