Stray light presents a continuing problem to the optical engineer. It reduces image contrast, introduces spurious signals, and in cases where a strong extraneous source is present, can completely mask the light from a weak object. Attempts to reduce or eliminate scattered light are often empirical and usually not very successful. Recently, however, powerful analytical techniques such as GUE RAP and APART have been developed to aid in system design. Using these techniques, which were described in a SPIE seminar on 'Stray Light Problems in Optical Systems," and are now published in SPIE Proceedings Volume 107 (1977), significant advances have been made in optimizing baffle design and improving system performance. The computer models, however, are only as good as the data fed into them, and there is no substitute for accurate knowledge of the scattering behavior of optical surfaces and the performance of optical blacks.