Dr. Perry is a world leader in research on turbulent flow. His major contributions are: (1) Development of existing and invention of new (e.g. the flying hot-wire anemometer) instrumentation. A book on this subject has been published. (2) Extensive novel experimental work especially on rough-surface boundary layers. The flying hot-wire is providing new insights into turbulent structure. (3) Development of new theoretical ideas for interpreting measurements. Outstanding contributions are the application of bifurcation ideas to turbulent flows and consideration of the role of discrete (coherent) vortices in turbulent flows