Abstract: A hybrid ion mobility and time-of-flight mass spectrometer includes an ion source region coupled to an ion mobility spectrometer (IMS) which feeds directly into an ion accelerating region of a time-of-flight mass spectrometer (TOFMS). In one embodiment, the TOFMS is positioned relative to the IMS so that the flight tube axis of the TOFMS is perpendicular to the drift tube axis of the IMS. In an alternate embodiment, the TOFMS is positioned relative to the IMS so that the flight tube axis of the TOFMS is non-perpendicular to the drift tube axis of the IMS. In the alternate embodiment, a known quadrupole ion trap is positioned between the IMS and the TOFMS to provide the capability of controlling the injection of ion packets into the TOFMS. The ion source may be a MALDI source, an electrospray ionization source, or an ion trap positioned between the IMS and any known ion source. In each case, the IMS, TOFMS and ion sources are preferably controlled by a computer.