Microbial quality of rainbow trout surface tissue (Oncorhynchus mykiss) and production ponds water where it is produced in northwestern Chihuahua state, Mexico, was assessed in trouts (200 fishes) and water (260 sampling) from nine fast stream, thirteen concrete and six dirt fish ponds during summer and winter seasons. Microbial quality was determined by measuring aerobic mesophiles, total coliform count, faecal coliforms and Salmonella spp., samples from the deep washing of the fish surface and the ponds. Temperature and oxygen content of water were also measured. The results for trout washing water indicated only significant differences (P<0.05) for aerobic mesophiles between seasons (398.11 CFU/mL in winter and 19,489.45 CFU/mL in summer), Salmonella spp. was not present in any fish or pond water samples. Aerobic mesophiles showed also higher numbers in water for summer season at water entrance, middle and discharge points of the different fish production ponds. Water temperature and oxygen content were always inside the normal range values considered for trout production in the three types of ponds, but water oxygen content showed significant difference (P<0.05) between the fast stream and dirt pond systems. It can be concluded, from the results obtained that surface tissue of the trout produced in the studied mexican northwestern Chihuahua State, ponds has excellent quality, having very low microbial counts and that water discharged from the production systems evaluated do not deteriorate the ecosystems, according to the government present regulations.Con el objetivo de caracterizar la calidad microbiológica del cultivo de la trucha arco iris (Oncorhynchusmykiss) (200 peces) y del agua de producción (260 muestras) de la misma, se muestrearon en la región noroeste del Estado de Chihuahua, 9 granjas con sistema de producción de corriente rápida, 13 con sistema de concreto y 6 con sistema rústico, en dos épocas del año (invierno y verano). Se determinaron de la superficie de los pescados y del agua: Mesófilos aerobios, Salmonella spp., coliformes totales y fecales, además de la temperatura y el oxígeno. Los resultados encontrados indican que en la trucha sólo hubo diferencias entre época (P<0.05) para mesófilos aerobios (398.11 UFC/mL en invierno y 19,489.45 UFC/mL en verano), no se aisló Salmonella. Se encontró efecto de época para mesófilos aerobios en el agua de entrada, estanques y salida, siendo superior en verano; la temperatura y oxígeno son normales para este cultivo con diferencias (P<0.05) en el nivel de oxígeno entre los sistemas de corriente rápida y rústico. En conclusión la trucha producida en esta zona tiene buena calidad microbiológica superficial y el sistema de producción no deteriora el ecosistema de acuerdo a las regulaciones vigentes
