Laser action is currently limited by device efficiency, rather than peak current density, is one conclusion drawn from this investigation of optically pumped light-emitting diodes (LEDs) made of conjugated polymers. The structure of the LEDs has been optimized to allow high current operation using short drive pulses. Unexpectedly high current densities and high luminous efficiencies at these current densities allow a high peak bright ness of 5 x 10(6) cd/m(2); see also the cover of this issue. The implications of these results for the fabrication of injection lasers are discussed.