Operation of an incoherent-scatter radar at Sonfre Stromfjord, Greenland, began in early February 1983, marking the beginning of a new effort in ground-based ionospheric research in the vicinity of the polar cusp and polar cap. The Sondrestrom Radar is located north of the arctic circle on the west coast of Greenland near the Sondrestrom Air Base at an invariant latitude of 75¿. The effects of the polar cusp may frequently be observed at local noon: the radar-measured signature in the F region is an increase of more than a factor of two in electron density. Additionally, the daytime variations in the F1-region electron density are dramatic. In contrast to auroral zone measurements, enhanced electron density at 150-km altitude has been observed and a marked absence of detectable E-region ionization at night has also been noticed.