The large thermal contrast between the cold atmosphere and the relatively warm ocean in springtime leads results in rapid ice growth and large fluxes of heat from the ocean to the atmosphere and of salt from the ice to the ocean. However, the magnitude of the ice growth and of the fluxes is moderated by solar radiation absorbed in the ice and upper ocean. During the Arctic lead experiment (LeadEx) we monitored ice conditions at four springtime leads during the first few days of growth. The experiment took place in March--April 1992 in the Beaufort Sea (73 ¿N, 146 ¿W). Two of the leads were <200 m in width, one was approximately a kilometer wide, and the fourth was quite large, more than a few kilometers wide. Ice thickness typically increased rapidly, with 15--20 cm of growth in the first few days. The crystallographic analysis of a series of ice cores taken across and along the edge of one of the smaller leads indicated that granular ice was more abundant along the edges (30%) of the lead than in the central part of the lead (10%). Observations suggest that thermodynamics processes dominated ice growth in these leads. Additional thickening of the ice at the edge of the leads was common because of rafting of the young ice and the accumulation of blowing snow. Ice temperature profiles exhibited a diurnal cycle induced by solar radiation, with daily oscillations of roughly 5 ¿C observed in the interior of the lead ice. Theoretical simulations for one lead indicated that during the first few days of ice growth, 30% of the incident solar irradiance was absorbed in the ice and 25% was absorbed in the upper ocean. The total amount of solar energy absorbed in the ice during this period was roughly equivalent to 4 cm of ice growth. The solar heating in ice and water is roughly comparable in magnitude to the net longwave and is approximately two thirds of the turbulent fluxes. ¿ 2000 American Geophysical Union