Measurements of 7Be specific activities in ground level air have been carried out at Fullerton, California, for a 23-month period from September 1973 through July 1975. The mean specific activity observed at this relatively dry location (less than 37 cm of annual total precipitation) was 0.216 pCi/m3. From this result a mean tropospheric residence time for 7Be-bearing aerosols of 35.4 days is obtained. This result is in very good agreement with residence times obtained from earlier measurements of 7Be and 7Be/32P ratios in rainwater.