We have prepared thin films of arc discharge single walled nanotubes by vacuum filtration. For film thicknesses greater than 40 nm, the films are of high optical quality; the optical transmission varies by <2% over the film area when measured with a spatial resolution of 4 mu m. However, the films become spatially non-uniform for film thickness below 40 nm. The in-plane DC conductivity correlates with the uniformity, increasing from similar to 3800 S/m for a 10 nm thick film to similar to 2-2.5 x 10(5) S/m for films of thickness >40 nm. Conductive atomic force microscopy maps show reasonably uniform current flow out of the plane of the film. For all thicknesses, the optical transmittance scales with film thickness as expected for a thin conducting film with optical conductivity of 1.7 x 10(4) S/m (lambda = 550 nm). For films with t > 40 nm the ratio of DC to optical conductivity was sigma(DC)/sigma(OP) = 13.0, leading to values of transmittance and sheet resistance such as T = 80% and R(S) = 110 Omega/square for the t = 40 nm film. Electromechanically, these films were very stable showing conductivity changes of <5% and <2% when cycled over 2000 times in compression and tension respectively. (C) 2009 Elsevier Ltd. All rights reserved.