The spatial distribution of marked Formosan subterranean termites was described immediately after release inside an experimental arena, using empirical distribution functions. Cohorts of 1,000 workers and 10% soldiers collected from field colonies were released in experimental arenas constructed of two of two sheets of transparent Plexiglas (105 x 105 cm) and filled with moisten sand, allowing them to build tunnels for three days. After this time, 50 termites marked with Nile Blue were released in the center chamber of the arena and digital photographs were taken every 10 s for 5 minutes for the 4 samples to measure distances between marked termites. The distances were used to calculate K(d), G(d), and F(d), that represented the expected number of marked termites within a distance d of another marked termite; how close are the marked termites from each other and from the boundaries of the arena; and how close are the marked termites to a hypothetical grid of regularly distributed points inside the arena, respectively. The null hypothesis that the arrangement of marked termites in the arena is consistent with complete spatial randomness (CSR) was tested with a Monte Carlo technique calculated from 99 simulations. The marked termites were distributed at random 66 of the 86 cases evaluated. This may an indication that marked termites have an equal probability to be located in the net of foraging galleries, a requisite to estimate the size of their foraging populations.