A new stereo-dual particle-image-velocimetry (SD-PIV) system for measurements in complex unsteady flow has been developed. Designed for measurements of shock-wave/boundary-layer interactions with separation control in particular, our system needs to fulfill demanding requirements: sufficient spatial and temporal resolution to cover the large range of characteristic frequencies O (100 Hz–100 kHz), an extended field of view to be able to analyze spatio-temporal links across the flow field, high laser-pulse energies, and access to all three turbulent velocity components. A suitable system is achieved by means of a multi-plane approach, using a SD-PIV system consisting of two synchronized stereo PIV systems that are carefully aligned to observe the same field of view. Measurements at several pre-selected temporal delays between the systems provide access to temporal characteristics of the flow. A frequency-based image separation was used to avoid laser cross pollution. The quality of the measurement system and the obtained data is demonstrated on the basis of measurements in three different configurations with large-scale flow separation: a low-speed forward-facing-step configuration and a high-speed shock-wave/boundary-layer interaction with and without separation control.