The Cornell storage ring CESR, designed to collide one bunch of e/sup +/ with one bunch of e/sup -/ at energies up to 8 GeV each, is used almost exclusively for research on b-quark physics (the /TAU/ region, 4.5 - 5.6 GeV per beam). Here the radiation loss is less than one-quarter the design maximum--low enough to relax beam-current limitations due to total rf power, yet still high enough to provide a comfortable amount of radiation damping (/tau/ /SUB rad/ approx. = 22 ms), which helps control beam instabilities. Performance is therefore relatively good. With single bunches, the luminosity (which scales roughly as E/sup 4/) reaches about 1.6 x 10/sup 31/ cm/sup -2/s/sup -1/ at 5.4 GeV. This is achieved with bunch currents of about 17 mA, in a regime where vertical beam blowup due to the beam-beam interaction makes L alpha I rather than I/sup 2/. The beam current is limited to this level by the onset of sudden beam losses during collision. To raise the luminosity, CESR has since 1983 operated with multiple bunches in each beam. At the unwanted crossing points within the guide-field arcs, these bunches are separated in the horizontal plane: e/sup +/ and e/supmore » -/ orbits are oppositely distorted, ''pretzel'' fashion, by a pair of electrostatic separators near the ends of each arc. The orbits still coincide around the two interaction points, and must do so very accurately of course. The required modifications of CESR, and early experience with multibunch operation, were described previously. We report our progress here, as an example of the considerations applying when two beams are bedded sideby-side in the same aperture, separated by electrostatic steering elements. The topics are: design constraints, Sec.2; lattice-optical and orbit effects, Secs. 3 and 4; and beam performance, Secs. 5 and 6.« less