The methods of probability theory are used to develop probabilistic models for predicting the total settlement (based on either consolidation test data or the results of standard penetration tests) and the time rate of settlement for a compressible clay layer in terms of uncertain values for soil compressibility and loads. The total settlement and the time rate of settlement are well approximated by log-normal distributions. Results calculated by use of the probabilistic approach are compared with settlement values measured in a well documented case history with good supporting laboratory test data.