The authors discuss more than twenty years experience using passive microseismic monitoring techniques to monitor the behaviour of oil and gas reservoirs, underground openings (both mining and structural), and natural/artificial slopes. In the majority of these instances logistical and cost constraints have necessitated the dispersal of groups of sensors and their associated acquisition units. Under some circumstances this can give rise to complex problems when the data has to be recombined prior to processing. However, these problems are relatively minor when weighed against the cumulative benefits which accrue to the operations as a result of the utilization of high quality microseismic data acquired from an extensive sensor array operated for an extended period.