Perfusion chambers employing laminar flow have dead volumes and unstirred layers which limit the minimum time required to effect a change in the local chemical environment of the sample. We have fabricated and tested a chamber capable of developing turbulent flow at reasonable flow rates of aqueous solutions. Transition to turbulence occurred at approximately equal to 1 mLs-1. To minimize dead space, a dual-exit cross-flow pattern was employed. The chamber was designed to mount on optical microscope stages for visual sample observation supplemented by a variety of techniques, such as fluorescence, light scattering and electrochemical monitoring. As indicated by fluorescence from a fluorescein-labelled protein film adherent to the chamber wall, local pH changes were produced within 200 ms. Use of the chamber is illustrated by measurements of stopped-flow kinetics in both calcium-triggered cortical granule exocytosis and influenza virus haemagglutinin-mediated cell-cell fusion.