The dewetting of thin films of low molecular weight diblock and triblock copolymers of poly(oxyethylene)/poly(oxybutylene) on silicon has been studied using video microscopy and X-ray reflectivity. Dewetted films were observed to comprise polygonal domains of polymer droplets, with a domain size of several millimeters. The dewetted films were studied using Xray reflectivity, which showed that a film of polymer <50 Angstrom thick remains on the substrate at the same time as the macroscopic droplets. This suggests that autophobic dewetting occurred in this system; i.e., a microscopically thin film was in equilibrium with macroscopic droplets. The growth velocity of holes in the polymer film was found to be constant at a fixed temperature in the stage of hole growth that could be studied using optical microscopy. The velocity was found to be an exponential function of temperature,