Sea ice leads are linear fracture zones in Arctic pack ice caused by divergent sea ice motion driven by wind and ocean currents. In winter， leads that are the main factories of ice formation and brine rejection， serve as the prime window for heat and material exchange between the Arctic Ocean and atmosphere. Spring onward， solar shortwave radiation transmitted through leads promotes the bloom of ice algae and plankton and subsequently sustains a habitat for wildlife in the Arctic. In summer， meltwater from sea ice floats on the ocean surface and usually converges to a reservoir of leads. In practice， the ocean surface in open leads is a crucial reference for satellite altimetry because it provides pathways for surface vessels and migration corridors for marine animals. Leads can be detected in optical， thermal， and microwave remote sensing images utilizing the contrast in their albedo， surface temperature， emissivity， and roughness from the surrounding pack ice. Various satellite and airborne images with moderate and high ground resolution have been used to evaluate the presence of leads. The products of lead distribution in the Arctic have been generated using different satellite remote sensing techniques. As sea ice in the Arctic becomes thinner and retreats earlier in the melt season， changes in the spatial and temporal distributions of leads can be expected. A recent study using MODIS thermal images has confirmed the continuous rise of spring lead areas in the Beaufort Sea since 2001， although for the entire Arctic， the results are still inconclusive. In the context of declining sea ice， the energy budget in leads must be parameterized based on comprehensive observations. The contribution of both open and refreezing leads to a regional energy and mass balance of sea ice， and its role in the changing Arctic climate and marine system， remains to be recognized.