slope can add significant value. Recent technological advances have enabled the routine use of this technique, yielding three-dimensional quantitative information about the state of the slope. A simple numerical model has been constructed of an open pit slope and the results are discussed in light of the fact that recorded seismic events can be located some hundreds of meters behind the slope surface. Seismic movements of known geological structures within the slope can be recorded and potentially used to assess trends in relative stability. It should be possible to indicate previously unknown structures using microseismic data, which may then be confirmed by other geotechnical techniques. The effects of complex geology and geometry on recorded seismic data have been studied and a composite focal mechanism method has been used to constrain possible fault plane orientations. Appropriate source spectral models for open pit seismic events have been discussed. Two case studies show that surface movements inferred from microseismic data enjoy a close spatial correlation with actual surface movements, with an advance indication of some 30-45 days. The paper shows that carefully analysed microseismic data from open pit slopes can be used to gain greater insight into the effects of mining and subsequently can result in more accurate assessments of slope stability. Microseismic Monitoring of Open Pit Slopes