The transport of nitric oxide (NO) in various plasticized and unplasticized polymeric films (silicone rubber, plasticized and unplasticized polyurethane, plasticized poly(vinyl chloride) and plasticized cellulose triacetate) is examined, and apparent NO diffusion coefficients are reported for each of the polymer compositions studied. Diffusion coefficients are found to range from ca. 2.5 x 10(-6) cm(2)/s in low weight percent plasticizer films to 3.0 x 10(-5) cm(2)/s in silicone films. The variation in NO diffusion rates through different polymer systems is explained by considering the characteristics of the polymers and, when applicable, the influence of plasticizer content. The newly measured values reported here should promote the rational choice of appropriate polymeric matrices for specific NO mass transfer applications.