In this paper, the water quality, diversity and distribution of aquatic insects in the middle and upper sub-basin of the river Mula, Bugaba, Chiriqui, Panama, is studied for the period March to July 2006. The samples were collected with entomological forceps and a type of D-net with a mesh of 1 mm. All the specimens were preserved in 70 % alcohol and a few drops of glycerin. A total of 2 832 aquatic insects were collected, grouped into 58 genera (12 undetermined), 34 families (one undetermined), belonging to eight orders of the Class Insecta. The diversity Shannon-Weaver index was 3,13, which shows high diversity in this ecosystem, where genus Rhagovelia sp. showed the higher abundance. According to the Jaccard similarity index, based on the presence of different genera identified, was obtained that stations 2 and 3 showed high similarity (54,2 %), while stations 1 and 4 had low similarity (14,7 %). The biotic index for the four stations showed values of 99, 169, 181 and 104. This indicates that the waters are slightly polluted at station 1, while at stations 2 and 3 waters are very clean and at station 4, the waters are clean.