Large concentrations of OVOC are present in the global troposphere and are expected to play an important role in atmospheric chemistry.  We measured a number of OVOC and tracers during an airborne experiment performed over the Pacific troposphere in the Spring of 2001.  These data are combined with other observations and interpreted with the help of a global 3-D model to assess OVOC sources and sinks.  In many cases, measured concentrations are uncertain and incompatible with our present knowledge of atmospheric chemistry.  We further interpret atmospheric observations with the help of an air-sea exchange model to estimate very large seawater concentrations of OVOC.  An extremely large oceanic reservoir of OVOC, that exceeds the atmospheric reservoir by more than an order of magnitude, can be inferred to be present.  We conclude that OVOC sources are extremely large (150-500 TgC y-1) but remain poorly quantified.  Results based on observations from several field studies and critical gaps will be discussed.