  We report on the status of the Novosibirsk experiment on a precision
measurement of the ratio $R$ of the elastic $e^+ p$ and $e^- p$ scattering
cross sections. Such measurements determine the two-photon exchange effect in
elastic electron-proton scattering. The experiment is conducted at the VEPP-3
storage ring using a hydrogen internal gas target. The ratio $R$ is measured
with a beam energy of 1.6 GeV (electron/positron scattering angles are $\theta
= 55 \div 75^{\circ}$ and $\theta = 15 \div 25^{\circ}$) and 1 GeV ($\theta =
65 \div 105^{\circ}$). We briefly describe the experimental method, paying
special attention to the radiative corrections. Some preliminary results are
presented.
