The kaon electroproduction reaction 1 H(e, e K + ) was studied as a function of the virtual-photon fourmomentum, Q 2 , total energy, W , and momentum transfer, t, for different values of the virtual-photon polarization parameter. Data were taken at electron beam energies ranging from 3.40 to 5.75 GeV. The center of mass cross section was determined for twenty-one kinematics corresponding to Q 2 of 1.90 and 2.35 GeV 2 , and the longitudinal, σ L , and transverse, σ T , cross sections were separated using the Rosenbluth technique at fixed W and t. The separated cross sections reveal a flat energy dependence at forward kaon angles not satisfactorily described by existing electroproduction models. Influence of the kaon pole on the cross sections was investigated by adopting an off-shell form factor in the Regge model, which better describes the observed energy dependence of σ T and σ L .Understanding the structure of nuclei and the interaction between nucleons in terms of subnucleonic degrees of freedom (quarks and gluons) is the goal of intermediate-energy nuclear physics. The advantage of electron scattering is that the one-photon exchange is a good approximation and can be calculated precisely [1]. This allows factorization of the electron and hadron dynamics in the electroproduction cross section.It is generally accepted that at four-momentum transfers, Q 2 1 GeV 2 , the virtual photon probes the subnucleonic structure of the hadron (see, e.g., Ref.[2]). Electron beams in the energy range used at the Thomas Jefferson National Accelerator Facility (JLab) therefore can access the subnucleonic structure of hadrons. However, these energies probe only nonperturbative aspects of QCD. In the nonperturbative 0556-2813/2010/81(5)/052201 (5) 052201-1