The electron density, ion temperature, and velocity measured on November 18, 1981, from 1100 to 1700 UT by EISCAT facilities exhibited clearly periodic behavior. We present an attempt to interpret this feature as a manifestation of gravity waves. November 18 was a day of high magnetic activity, and it was difficult to separate completely the local effects from those induced by the gravity waves. The observed waves had a period of about 75–80 min and vertical wavelength of the order of 800 km. They were possibly generated in the auroral oval, about 1000 km from Tromsø.