Although mass spectrometry is in general one of the most sensitive spectroscopic tools available to the analyst, frequently providing useful data on 1 microgram or less of material, in many cases it is desirable to attempt confirmation of gas chromatographic effluents of known structure by this technique at concentration levels of the nanogram range or less. A potentially important application in which such enhanced sensitivity would be particularly useful is pesticide residue analysis since residues at picogram and nanogram level are often encountered. The present communication describes the interfacing of a small laboratory time averaging computer with a combination gas chromatograph-mass spectrometer, allowing repetitive scanning and averaging of mass spectra peaks, subtraction of background peaks, normalization, and printout in plotted form, and the applications of this system for the confirmation of pesticide residues of known structure.