For many applications of time-domain spectroscopy it is desirable to improve the time resolution of electron-optical streak cameras to less than 200 fs in the u.v. visible and i.r. and to ca . 1 ps at X-ray wavelengths. A suite of interactive computer programs has been developed for electron-optical design, taking into account time dispersion. It is possible to analyse rapidly the details of both spatial and temporal imaging properties of currently available streak tubes and to optimize the designs for particular applications. The computed results are shown to be in excellent agreement with the experimental values for the Photochron II streak tube. The expected performance characteristics of a preliminary design for a new tube, the Photochron III, are given.