Wedemonstratedexperimentallytheformationofmonoenergeticbeamsofacceleratedelectronsbyfocusingfemtosecondlaserradiationwithanintensityof2×1017W/cm2ontotheedgeofanaluminumfoil.Theelectronshadenergydistributionspeakinginthe0.2–0.8MeVrangewithenergyspreadlessthan20%.Theaccelerationmechanismrelatedtothegenerationofaplasmawaveasaresultofself-modulationinstabilityofalaserpulseinadenseplasmaformedbyaprepulse(arriving12nsbeforethemainpulse)isconsidered.One-dimensionalandtwo-dimensionalParticleinCell(PIC)simulationsofthelaser–plasmainteractionshowedthateffectiveexcitationofaplasmawaveaswellastrappingandaccelerationofanelectronbeamwithanenergyontheorderof1MeVmayoccurinthepresenceofsharpgradientsinplasmadensityandinthetemporalshapeofthepulse.