The electron injection rate of bis(Bu4N) cis di(thiocyanato) bis (2,2'-bypiridine-4,4' carboxylic acid)Ruthenium (II) dye (N719) into SnO2 nanocryst. thin films was measured with 2-color femtosecond transient absorption spectroscopy. The electron injection rate was obtained by monitoring the formation of the oxidized state of the dye and the arrival of electrons in the conduction band. Dynamics of electron injection are multiexponential (0.2, 4 and 130 ps) and are therefore slower than the N719-ZnO or N719-TiO2 systems. The photocurrent action spectrum of N719-SnO2 shows a quantum efficiency of 0.65 at 530 nm proving that efficient charge sepn. can take place despite the relatively slow electron injection rate.