Description: The main objective of this research paper is to estimate the new-ice production in the Laptev Sea flaw lead during the 1991/1992 winter season. A one-dimensional energy balance model was applied to calculate ocean-to-atmosphere heat flux and the resulting new-ice formation over open water. For a detailed estimate of regional ice production, the flaw lead was divided into 14 sections based on the analysis of NOAA-satellite images and Russian ice charts. Opening and maintenance of the lead sections are controlled by offshore winds, whereas closing of open water is caused by onshore winds. Since the orientation of the lead varies from section to section, the same regional wind forcing can cause different local lead behavior. Model results reveal that the seasonally accumulated thickness of new ice formed in the different lead sections—under the assumption of instantaneous lateral new-ice removal from the water surface—varies from 1.3 m to 13 m over temporarily open water and may reach 20 m over permanently open water. The corresponding ice volume produced in the sections varies between 3.4 km3 and 59 km3 and amounts to 258 km3 for the entire lead. The significant regional variations in new-ice production are due to differences in (i) the number of days that a lead section is open (open-lead days), (ii) the oceanic heat loss during open-lead days, and (iii) the areal extent of the lead sections. As compared to other studies,—at least during 1991/1992 winter season—the Laptev Sea flaw lead produced between 28 and 617% more initial sea ice than the Kara, Barents, East Siberian and Chukchi leads. Despite its limited areal extent of roughly 36,000 km2, which represents only 8% of the entire Laptev Sea, the flaw lead produces about 32% of the annual shelf ice. The ice production in the flaw lead is 5.3 times higher than the remainder of the shelf (7.4 m vs. 1.4 m). Furthermore, the Laptev Sea flaw lead produces 2.6% of the ice annually formed the entire Arctic Mediterranean Sea and contributes about 9% to the volume of the Siberian branch of the Transpolar Drift Ice System. This makes the Laptev Sea flaw lead a significant producer of Arctic sea ice on local and regional scales, whereas the contribution of lead ice to the entire volume of annually formed pack in high northern latitudes amounts only to roughly 1.3%.