This study assessed the level of secondary production in the Muskeg River and tested the validity of hypotheses generated by Crowther and Griffing (1979) regarding the trophic structure and function of the Muskeg River as a "typical" tributary of the Alberta Oil Sands Environmental Research Program study area. A trophic rather than a taxonomic approach to aquatic invertebrate classification was taken and a modification of the Hynes method was used for the calculation of production. The disadvantages and advantages of these methods are discussed. It was found that secondary production in the Muskeg River was highest upstream by a factor of two times that of a central site and four times that of a downstream site. These production values are compared to benthic production in other researched rivers. The production values are considered assessments of the levels of secondary production instead of true estimates. Reasons for this are discussed and the trophic compartmentalization of production is presented. The data also showed that the trophic economy of upstream sections of the river was based upon detrital and algal feeding and their importance decreased in a downstream direction, whereas the importance of carnivores and omnivores increased in a downstream direction. This was based upon the availability of coarse particulate organic matter (CPOM) at upstream sites, which was degraded to fine particulate (FPOM) and refractory particulate organic matter (RPOM) and exported downstream. These findings are in agreement with the hypotheses generated by Crowther and Griffing (1979). The reasons for the trends in secondary production and the shifts in community structure within each river reach are discussed. Finally, recommendations are given for further studies in the AOSERP study area, since this area may be impacted in the future by oil sands development.