Microwave radiometric temperature (TB) profiles of first-year sea ice were obtained along 70- to 100-m traverse, with sled-mounted radiometers at 10, 18.7, 33.6, and 37 GHz and an effective spot size of 30 cm. Measurements of TB as a function of nadir angle were obtained at selected sites along the traverses. Snow and ice properties were recorded and correlated with the TB measurements to infer the effect of snow cover and ice conditions on the radiometric temperature. TB correlated positively with the brine volume profile in the ice at several sites, suggesting that brine volume has a strong effect on TB under these conditions. An overall statistical comparison of snow thickness with TB, when compared with previously published models, suggests that the effect of snow cover on the microwave transmission coefficient of the snow/ice interface may be an important contribution to the radiometric temperature at these frequencies. A model is proposed to explain the data.