Mercury porosimetry was performed on 92 hardened cement paste specimens of water/cement (w/c) ratios 0.3, 0.4, 0.5, 0.6. and 0.7 and curing times of 1, 3, 7, 14, 28, and 56 days. This paper presents the experimental techniques, results, and their possible implications with respect to pore connectivity. As expected, longer curing times and lower wic ratios resulted in smaller indicated total porosities and smaller threshold pore widths. Longer curing times and higher wic ratios resulted in greater degrees of hydration. In most of the mercury intrusion results, two peaks could be observed in the differential curves that were identified as the "initial" and "rounded" peaks. The initial peak may correspond to the intrusion of mercury through a connected capillary network, while the rounded peak may correspond to the crushing of interposed hydration products. (C) 1999 Elsevier Science Ltd. All rights reserved.