Data from a combined ion line/plasma line incoherent scatter experiment with the European incoherent Scatter (EISCAT) UHF radar are used to derive the ion-neutral collision frequency in the lower E region (101--114 km). The ion line measurement is based on a 5--14 &mgr;s multipulse scheme giving a range resolution of 3 km. A spectrum analyzer is used to measure plasma line signals from the same altitudes. A 1-hour period at local noon where stable photoelectron enhanced plasma lines were detected is chosen for the analysis. The temperature/collision frequency ambiguity in the ion line autocorrelation function is resolved by incorporating the observed plasma line offset in the least squares fitting procedure. No assumption on the electron-to-ion temperature ratio is needed. The fitted collision frequencies compare well with a profile based on the mass spectrometer/incoherent scatter (MSIS) 1983 neutral atmosphere model. ¿ American Geophysical Union 1989