In order to grow, organisms must acquire adequate amounts of carbon (C), nitrogen (N) and phosphorus (P) from their food. Growth can be limited by the relative supply of these nutrients, especially in aquatic ecosystems. In streams, the growth of aquatic insects has been shown to be influenced by thermal regime, food quantity and conspecific density. In this study, we assessed the growth of a common suspension-feeding caddisfly (Brachycentrus occidentalis) from a stoichiometric perspective by comparing the elemental composition (C:N:P) of the organism to its food (seston). We analyzed C:N:P ratios of B. occidentalis body tissue and seston from four streams in southwestern Wisconsin. Samples were collected in summer and fall of 2004 and in late winter of 2005. The instantaneous growth rate (IGR) of larval B. occidentalis was also estimated. The IGR of B. occidentalis differed among the four streams, even though the streams possessed nearly identical thermal regimes. These differences appear to be correlated to the C:P and N:P imbalances between the larvae and the seston; B. occidentalis IGR was greater when elemental imbalances were greater (i.e., when seston had less carbon and nitrogen per unit phosphorus).