It is suggested that multi-mode slab waveguide spectrographs, developed for wavelength division multiplexing (WDM) in optical communications, might have a role in astronomical instrumentation. A stack of such waveguide devices could form an effective instrument for multi-object spectroscopy. The performance of some existing devices is described, and their applicability to astronomy investigated. It is found to be limited. However, it is shown that only a modest improvement in resolution (by a factor of 2 - 4), together with a realization of the potentially very high optical efficiency, could yield an astronomically-useful device. The problems anticipated in developing such an instrument are outlined.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.