Tracking at high intensities

High crossing rates and complex event structure impose stringent demands on tracking detector techniques and layouts, as do the requirements of precision and stability, radiation hardness, and the need to minimise material and heat loads. Experiments with long lead times must be robust enough in design to satisfy physics targets beyond those initially specified. The use of tracking information in triggering and lepton identification is considered in this light. The discussion focuses on gaseous techniques in use at or proposed for the high-rate HERA and LHC colliders.