In this contribution the first measurements of a single-shot femtosecond laser pump-probe technique are reported. The technique is based on counter-propagating femtosecond laser pulses in a supersonic beam of a low density of sample molecules and simultaneous probe detection by ion or fragment-ion formation through a reflectron time-of-flight mass spectrometer. It will be shown that the range of the pump-probe delays covers the time span between 100 fs and 10 ps depending on the pulse width of the laser used and the stability of the volt ages of the mass spectrometer. The application of this technique to organometallic compounds as well as to medium-sized organic molecules reveals some insight into the electron-transfer process during ionization through a 1+1 multi-photon absorption procedure. Furthermore it is demonstrated that this technique is also applicable to the investigation of ultra-fast isomerization and fragmentation processes. As an example the results of the processes within iron pentacarbonyl and substituted benzalacetones are reported.