Lepidopteran stem borers are a major constraint to food production in Kenya. Bt (Bacillus thuringiensis) maize is an effective and affordable option of stem borer management, which has the potential to increase food security in Kenya. However, before Bt maize is deployed in Kenya, there is need to address environmental concerns about this technology. One concern is its effect on non-target organisms. A prerequisite is to identify key non-target arthropods in major maize-growing regions in the country. This was done using an environmental risk assessment model (ERAM). On-farm studies were then conducted on five farms in each of the five maize-growing regions in Kenya: lowland tropics (Kilifi), dry mid-altitude (Machakos), moist mid-altitude (Embu), moist transitional (Kakamega), and highland tropics (Kitale), for two seasons to identify the major target and non-target arthropods of Bt maize. In each region, a typical maize-cropping system was selected, and the arthropods in it were monitored weekly using pitfall, water and sticky traps, and by destructive sampling of maize plants, three times a season. Target (stem borers) and non-target arthropods were identified and preserved in appropriate storage systems. The dominant stem borers in Kilifi were Chilo partellus and C. orichalcociliellus; in Machakos C. partellus and Sesamia calamistis; in Embu Busseola fusca and C. partellus; in Kakamega B. fusca and C. partellus; in Kitale B. fusca and S. calamistis. According to ERAM the major non-target arthropods recovered in each group were lepidopteran herbivores Helicoverpa armigera and Crytophlebia leucotreta and non-lepidopteran herbivore Prostephanus truncatus. The key parasitoids of stem borers were larval Cotesia flavipes and C. sesamiae and pupal Dentichasmias busseolae. The major predators were ants, ladybirds, earwigs and spiders. The major pollinator was the honeybee, Apis mellifera; the decomposer of organic matter was the earthworm. Voucher specimens of each of the arthropods collected were preserved in a reference collection, which is to be used as technical reference during the field monitoring phase on the effect of Bt maize on general arthropod diversity. The non-target effects to be examined for the respective arthropod groups are discussed.