A series of surface-based measurements of microwave brightness temperatures and accompanying ice characteristics have been made on first-year and multiyear sea ice in the Canadian archipelago and in the southeastern Beaufort Sea during the late spring and early summer of 1982. Radiometer data taken at frequencies of 10, 18.7, and 37 GHz show the transition from conditions of snow-covered ice from the onset of snow melt through to full summer melt conditions. Initially, values of TB for multiyear ice were larger than for first-year ice, but by the middle of the experiment this distinction disappeared. Drained surfaces often had emissivities above 0.95, but values dropped considerably lower during heavy melting events. The skewness of the distribution of TB appears to distinguish ice types further into the melt season. The standard deviation is not useful for ice type discrimination but is sensitive to the area covered by melt ponds. Microwave attenuation in various surface layers was found to range from 2 m-1 early in the experiment to >400 m-1 during fall summer melt, indicating penetration depths from 250 to 2.5 mm, respectively.