Surface diffusion parameters, the thin film growth mode, and thermal stability of indium deposited on a W {100} single crystal have been studied using LEED, TDS and scanning AES, the surface diffusion studies being of central importance as part of a programme to examine the effect of lateral adatom-adatom interactions on diffusion parameters. A correlation of LEED, AES and secondary electron yield (SEY) measurements during stepwise deposition of indium point to completion of a pseudomorphic indium monolayer before subsequent growth occurs. Following layers grow in a long-range disordered fashion. First layer growth initially takes place via random occupation of surface sites, with two-dimensional islands forming at higher coverages. TDS indicates that evaporation from a thick film occurs down to two monolayers (ML) over the relatively narrow temperature range 700 to 800 K, the desorption energy, 240 kJ mol −1, being close to the reported sublimation energy for indium. Desorption of the second and first monolayers occurs between 800 and 1200 K, indicating a strongly coverage-dependent activation energy for desorption. Up to a monolayer coverage both the activation energy for diffusion ( E m) and the diffusivity ( D 0) are strongly coverage-dependent, indicating net repulsive lateral adatom-adatom interactions (for θ = 0.25 ML, E m∗ = 106 kJ mol −1 while for θ = 0.75 ML, E m∗ = 64 kJ mol −1) . The activation energy for diffusion is roughly a constant fraction of that for desorption (≈ 30%) in the monolayer region. Second and subsequent layers of indium diffused much more rapidly than the first; in this case E m∗ and D 0∗ are insensitive to coverage, and the diffusion energy barrier is only 10% of the desorption energy.