Naturally occurring positive and negative ions in the troposphere have been mass identified at Sapelo Island, Georgia, and Mt. Evans, Colorado. These measurements were made at ground level under a variety of weather conditions. Over the course of the experiment, positive ions were seen at masses 54, 60, 80, and 94 AMU. Mass 54 AMU is believed to be NH4.2(H2O). In the negative spectrum, ions were observed at masses 62 and 125 AMU and are believed to be NO2 and NO3.(HNO3) Several ions that appear to be H2O clusters of the above ions were also observed. These are the first measurements of the mass identity (1-AMU resolution) of naturally occurring ions in the troposphere with the exception of a previous measurement made in 1982 over a limited mass range in an urban environment (Eisele, 1983). Ions that were artificially produced were also studied and compared to the much longer lived natural ions.