Because environmental impacts accumulate over space and time, their analysis is difficult, necessitating the incorporation of the most recent scientifically defensible information and methods into the process. A cumulative impact matrix is proposed that sets up additive, synergistic, and indirect categories, each capable of variation in space and time. Every interaction would be carefully examined to decide the likelihood of cumulative impact in any of the six categories. Because of its 'magnifying glass' approach, such a matrix could be a very useful analytical tool, using existing methods to uncover all the information presently available about the behavior of the ecosystem. (Copyright (c) 1988 Springer-Verlag.)