  This article summarizes a workshop held on March, 2014, on the potential of
the James Webb Space Telescope (JWST) to revolutionize our knowledge of the
physical properties of exoplanets through transit observations. JWST's unique
combination of high sensitivity and broad wavelength coverage will enable the
accurate measurement of transits with high signal-to-noise. Most importantly,
JWST spectroscopy will investigate planetary atmospheres to determine atomic
and molecular compositions, to probe vertical and horizontal structure, and to
follow dynamical evolution, i.e. exoplanet weather. JWST will sample a diverse
population of planets of varying masses and densities in a wide variety of
environments characterized by a range of host star masses and metallicities,
orbital semi-major axes and eccentricities. A broad program of exoplanet
science could use a substantial fraction of the overall JWST mission.
