Ultrafast eleotro-oplic sampling technique for characterizing ultrafast electrical transients is reported. The traveling wave Poekels, effect in electrooptic crystal and high repetition rate femtosecond dye laser system wore employed. Temporal resolution of less than Ips and voltage sensitivity of less than 50 uV have been obtained, and the electrical transients of Cr:GaAs photoconductive switch and dispersive characteristics of stripline transmission lines were measured.