In an effort to determine the aquatic insects in the Santa Maria river mid-low watershed, a set of samples were collected from April 2002 to April 2003 in 13 sampling stations along 50 km of the river mid-low section. Different capture methods were used according to substrate and dredge of river floor. D-net was used to perform bottom scans and search for insects in sub-aquatic vegetation; forceps were used to remove samples from leaf litter and rocks. The aquatic insect community found in the Santa Maria river mid-low section was represented by 56 genera, of 32 families and 7 orders: Hemiptera, Odonata, Coleoptera, Ephemeroptera, Trichoptera, Diptera, and Neuroptera.