A simultaneous generation of multiwavelength short pulses is demonstrated by self-injection seeding of a laser diode. The wavelengths are selected by the use of multiple optical paths in an external cavity consisting of a grating, a beam splitter, and two mirrors. By adjusting the grating and either one of the mirrors, the wavelengths and their spacings can be readily tuned in a flexible manner. The system is simple, robust, and is of low cost. ©1997 American Institute of Physics.