A combination of the frequency distribution of body sizes and appropriate allometric relationships may permit a more operational approach to pesticide bioaccumulation than the more traditional trophic level concept. To demonstrate this potential, we describe patterns of bioaccumulation as functions of time and body size in a computer ecosystem in which no differences in trophic level exist. The qualitative similarity between these patterns and those reported in the literature from laboratory and field experiments suggests that empirical relations describing contaminant fluxes as functions of body weight could form a powerful base for the prediction of contaminant body burden in natural systems. We believe this approach could prove useful for any persistent contaminant with high biological affinity.Key words: modeling, bioaccumulation, ecological magnification, allometry, body size