WATER QUALITY AT RIO DAS PEDRAS, WESTERN PARANÁ, USING BENTHIC MACROINVERTEBRATES AS INDICATORSABSTRACT: Benthic macroinvertebrates are widely used as bioindicators of water quality due to their physiological and morphological characteristics. The aim of this study was to evaluate the water quality at Rio das Pedras, in the city of Matelândia, Western Paraná, in the dry season, using benthic macroinvertebrates as bioindicators, and to identify the optimal time for the incubation of litter bags. Sixty litter bags were prepared with leaves from native trees from the riparian forest and incubated in Rio das Pedras river. Eight litter bags were collected at intervals of 3, 7, 14, 28, 35 and 42 days. The benthic macroinvertebrates were identified at the family level and the Biological Monitoring Working Party Score System index was applied. With this study, it can be concluded that the Rio das Pedras river has unpolluted waters, demonstrating that the system has hardly been changed. The litter bag incubation period in order to obtain the results for evaluating the water quality index for the Biological Monitoring Working Party Score System was of seven days, and the period to analyze the structure of the benthic macroinvertebrate community was of 28 days. KEY WORDS: Colonization. Litter bags. Incubation time. CALIDAD DE LAS AGUAS DEL RIO DAS PEDRAS, OESTE DEL PARANÁ, UTILIZANDO MACROINVERTEBRADOS BENTÓNICOS COMO BIOINDICADORES RESUMEN:Los macroinvertebrados bentónicos son ampliamente utilizados como bioindicadores de calidad del agua en todo el mundo, debido sus características fisiológicas y morfológicas. El objetivo de este estudio ha sido evaluar la calidad de las aguas del Rio das Pedras, en el municipio de Matelândia, oeste del Estado de Paraná, en la estación seca, utilizándose de macroinvertebrados bentónicos como bioindicador, e identificar el tiempo ideal de incubación de los litter bags. Sesenta litter bags han sido confeccionados con hojas de árboles nativas procedentes de la floresta ribera e incubados en el Rio das Pedras.Ocho litter bags fueron recogidos en intervalos de tres, siete, catorce, veintiocho, treinta y cinco y cuarenta y dos días. Los