Measurements of air samples taken near the ground at different locations in urban as well as in rural areas show the presence of acetonitrile (Ch3CN) in concentrations up to 7 ppbv. The measurements of this compound were carried out by a gas chromatographic method with an electron capture detector and by a mass spectrometric method with a GC-MS quadrupol mass filter system. The present results support tropospheric sources for acetonitrile recently found in stratospheric ion-clusters.