Exchange of heat and mass across deformable fluid-fluid interfaces is central to many industrial and environmental processes but is still poorly understood, despite the considerable effort that has gone into its studyuncertainties in greenhouse gas uptake estimates are still very large. This poor state of knowledge arises primarily because of interfacial scalar exchange being controlled by near-surface turbulence, which is difficult to measure and simulate as interfaces move, deform, and sometimes break. However, recent advances in particle imaging velocimetry and numerical approaches have led to some progress in this area. These studies indicate that liquid-side controlled gas exchange is well-predicted for clean, nonbreaking interfaces by surface renewal models in which the renewal frequency is that of turbulent sweeps that impinge on the interface. This, in turn, can be related to the interfacial stress, leading to useful parametrizations for exchange coefficients. For breaking conditions, such approaches break down and a theory that relates the divergence of the surface-velocity fluctuations to scalar exchange rates is found to be useful. Because the surface divergence can be remotely observed, this theory may allow more reliable global and regional estimates of air-water scalar exchange budgets.