Solvolysis of 9-(1-X-ethyl)fluorene (1-X, X = I, Br, Cl, OTs, or OBs) in 25 vol % acetonitrile in water gives the elimination products 9-(1-ethylidene)fluorene (3) and 9-vinylfluorene (2) and the substitution products 9-(1-hydroxyethyl)fluorene (1-OH) and 9-(1-acetamidoethyl)fluorene (1-NHCOMe). The iodide (1-I) and the bromide (1-Br) yield 3 as the main product by a solvent-promoted concerted E2 reaction (J. Am. Chem. Soc. 1995, 117, 1839), but the tosylate (1-OTs) and the brosylate (1-OBs) do not undergo any significant concerted reaction with the solvent. Added strong nucleophiles open up a competing bimolecular substitution pathway (S(N)2). The importance of this route is leaving-group-dependent; this "synergism" between nucleophile and leaving group favors S(N)2 reaction with I- > Br- > Cl- > OTs(-), OBs(-) leaving groups. A similar trend in leaving-group effects is observed for solvent- and base-promoted E2 reaction; e.g., 1-I, 1-Br, and 1-OBs yield 95%, 69%, and 0% solvent-promoted E2 reaction, respectively. The S(N)2/E2 ratio with thiocyanate as nucleophile/base increases in the series 1-I, 1-Br, and 1-OBs; the ratios were measured as 0.2, 0.7, and 3.2, respectively. The S(N)2 reactions with thiocyanate ion in methanol-water mixtures show small sensitivity to solvent "ionizing power"; e.g., with the deuteriated analogue (9-H-2)-9-(1-bromoethyl)fluorene (d-1-Br) a value of m = 0.20 was measured which can be compared with the value of m = 0.59 obtained for solvolysis through the ion pair.