Introduced in 1996, the Agilent (Hewlett Packard) HP 6890/5973 GC/MSD system is the latest of the bench-top GC/mass spectrometry (MS) family. Started with the HP 5970 MSD, introduced in the mid-1980s, has provided small/medium size laboratories with the power of a true MS that provides selectively and library-searchable capability. This paper presents study results on instrumental sensitivity achieved with the new MSD, with examples illustrating trace-level analysis of semi-volatile compounds such as PCB and Dioxins. Investigations were carried out to study the effect of some operational parameters such as ionisation energy, dynode voltages and dwell time. In the standard electron impact selected ion monitoring (SIM) mode, the new MSD can provide sub-picogram level sensitivity for chlorinated hydrocarbons. In scan mode, under optimal condition, the system can generate library-searchable spectra from sub-nanogram quantity of analytes. This sensitivity level rivals traditional GC with selective detectors such as electron capture detector but at the same time possesses the advantage of computerised library search against a database of over 100 thousand spectra. The relatively compact size makes the system practical in a mobile laboratory, providing qualitative as well as quantitative data in spill emergencies analyses.