Ultrashort pulses were produced at 248 nm by using a transverse-discharge KrF* excimer laser as a high-energy amplifier system. Input pulses for the amplifier system were obtained by upconverting the output of a modelocked visible dye laser to the ultraviolet by using nonlinear crystals. Pulses of up to 20 mJ; in energy with 10-30-psec duration were obtained at 10 pulses/sec. The output pulse width was characterized by using an electronic autocorrelator.