This paper examines the electron transfer (ET) photophysics of two pyrene-labeled nucleosides, 5-(1-carboxypyrenyl)-2’-deoxyuridine (1) and 5-(1-pyrenyl)-2’-deoxyuridine (2) by a variety of spectroscopies in several different solvents. For 1 in methanol (MeOH), a maximal change-in-absorbance (Delta A) increase at 460 nm characteristic of pyrene(.+) occurs during the time of photoexcitation (less than or equal to 30 ps). (A control experiment ensures that pyrene(.+) is formed from the singlet excited state of pyrene and not as result of multiphoton ionization of pyrene by the laser pulse.) The pyrene(.+) signal decays in 20-70 ps slightly more slowly than does the S-1 state’s positive Delta A signal at 510 nm. These results prove that the S-1 state of pyrene is quenched due to intramolecular ET. Similar results are also obtained for 1 in acetonitrile (MeCN) where the pyrene(.+) absorbance at 460 nm decays in ca. 100 ps. For 1 and 2, changing solvent from MeOH to MeCN increases both emission Lifetimes and quantum yields. For 2 the emission yield increases 13-fold, while for 1 it increases 3-fold. Even though the dielectric constants of MeOH and MeCN are similar, 33.6 and 37.5, respectively, both the large emission yield increase and the accompanying striking change in the emission spectrum for 2 on switching from MeOH to MeCN are consistent with lessened ET quenching due to raising the free energy of the pyrene(.+)/dU(.-) charge transfer product relative to the pi,pi* state of pyrene, where dU=2’-deoxyuridine. Since dU(H)(.) requires less energy to form than does dU(.-), ET quenching should be more favorable in MeOH, where dU(H)(.) can be formed, than in MeCN, where only dU(.-) can be produced. If this model is correct, the time of protonation of dU(.-) in MeOH is less than or equal to 30 ps for 1 based on transient absorbance measurements of the appearance of pyrene(.+).