Using a recently developed constant pressure ab initio molecular dynamics method for studying nonperiodic systems, we have investigated pressure-induced structural transformations in silicon clusters. Pressure is applied and tuned through a liquid described by a classical potential, while the clusters are treated within a density functional theory scheme. Pressure-induced transformations in the Si35H36 and Si71H60 clusters show common characteristics, with a tendency toward metallicity at high pressure and a hysteretic behavior when the pressure is released. (C) 2001 American Institute of Physics.