The characteristics of vacuum consolidation of soft clay soils are discussed. The results of laboratory odometer tests indicate that applying a vacuum pressure generally causes less settlement than applying a surcharge load of the same magnitude. It is demonstrated by both laboratory tests and theoretical analysis that in cases where the bottom of a soft clayey deposit is free draining, application of a vacuum pressure will cause less consolidation settlement than an equivalent surcharge load because of the drainage boundary effect. For this type of subsoil condition it is suggested that if vacuum consolidation is combined with the use of prefabricated vertical drains (PVDs) for ground improvement, the PVDs should not penetrate the entire clay layer. An equation for calculating the optimum penetration depth has been derived. In the field, vacuum consolidation causes inward lateral displacement while an embankment load will generally cause outward lateral displacement of the underlying soil. The combination of vacuum pressure with embankment loading can therefore substantially reduce preloading-induced lateral displacement of the subsoil. A full scale field test combining vacuum pressure with embankment load conducted at Bangkok, Thailand, and the corresponding analysis results are presented briefly to illustrate the effect of vacuum pressure loading on lateral displacements in the subsoil.