This paper presents the methodologies and results of two types of neural networks used to estimate the unconfined compressive strength (UCS) of weakly cemented sandstones from geophysical log data. The first neural network used 29 different logs as input and predicted UCS values at 8 cm depth resolution that were in good agreement with measured values. The second neural network used an innovative approach to improve the depth resolution and detection of thin bedding by relating changes in high resolution logs (e.g. bulk density or resistivity) to changes in strength. Preliminary analyses used to predict the undrained shear strength of marine clay illustrate the potential of this new approach for predicting the strength of weakly cemented sandstones. Copyright ASCE 2006.