The photoinduced (266 nm) ultrafast decarboxylation of the peroxyester tert-Bu 9-methylfluorene-9-percarboxylate (TBFC) in soln. has been studied with femtosecond time resoln. While the photodissocn. of TBFC occurs too fast to be resolved, the intermediate 9-methylfluorenylcarbonyloxy radical (MeFl-CO2) decarboxylates on a picosecond time scale. The latter process is monitored by pump-probe absorption spectroscopy at wavelengths between 400 and 883 nm. The measured transient absorbance signals reveal a dominant fast decay with a lifetime of a few picoseconds and, to a minor extent, a slow component with a lifetime of about 55 ps. Statistical modeling of MeFl-CO2 decarboxylation employing mol. parameters calcd. by d. functional theory suggests that the fast component is assocd. with the decarboxylation of vibrationally hot radicals, whereas the 55 ps decay reflects the dissocn. of thermally equilibrated MeFl-CO2 at ambient temp. The vast majority of MeFl-CO2 radicals thus decarboxylates on a time scale about an order of magnitude faster than expected from the time const. of 55 ps reported by Falvey and Schuster for this ref. reaction. This literature value turns out to refer to decarboxylation rate of MeFl-CO2 at ambient temp.